refactor: model message schemas after IRC RFC 1459/2812

Replace c2s/s2c/s2s taxonomy with IRC-native structure:
- schema/commands/ — IRC command schemas (PRIVMSG, NOTICE, JOIN, PART,
  QUIT, NICK, TOPIC, MODE, KICK, PING, PONG)
- schema/numerics/ — IRC numeric reply codes (001-004, 322-323, 332,
  353, 366, 372-376, 401, 403, 433, 442, 482)
- schema/message.json — base envelope mapping IRC wire format to JSON

Messages use 'command' field with IRC command names or 3-digit numeric
codes. 'body' is a string (IRC trailing parameter), not object/array.
'from'/'to' map to IRC prefix and first parameter.

Federation uses the same IRC commands (no custom RELAY/LINK/SYNC).

Update README message format, command tables, and examples to match.

schema/numerics/001.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/001.json",
+  "title": "001 RPL_WELCOME",
+  "description": "Welcome message sent after successful session creation. RFC 2812 §5.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "001" },
+    "to": { "type": "string", "description": "Target nick." },
+    "body": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "Welcome text lines."
+    }
+  },
+  "required": ["command", "to", "body"],
+  "examples": [
+    { "command": "001", "to": "alice", "body": ["Welcome to the network, alice"] }
+  ]
+}

schema/numerics/002.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/002.json",
+  "title": "002 RPL_YOURHOST",
+  "description": "Server host info sent after session creation. RFC 2812 §5.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "002" },
+    "to": { "type": "string" },
+    "body": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "Host info lines."
+    }
+  },
+  "required": ["command", "to", "body"],
+  "examples": [
+    { "command": "002", "to": "alice", "body": ["Your host is chat.example.com, running version 0.1.0"] }
+  ]
+}

schema/numerics/003.json

@@ -0,0 +1,36 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/003.json",
+  "title": "003 RPL_CREATED",
+  "description": "Server creation date. RFC 2812 \u00a75.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": {
+      "const": "003"
+    },
+    "to": {
+      "type": "string"
+    },
+    "body": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "Text lines."
+    }
+  },
+  "required": [
+    "command",
+    "to",
+    "body"
+  ],
+  "examples": [
+    {
+      "command": "003",
+      "to": "alice",
+      "body": [
+        "This server was created 2026-02-01"
+      ]
+    }
+  ]
+}

schema/numerics/004.json

@@ -0,0 +1,39 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/004.json",
+  "title": "004 RPL_MYINFO",
+  "description": "Server info (name, version, available modes). RFC 2812 \u00a75.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": {
+      "const": "004"
+    },
+    "to": {
+      "type": "string"
+    },
+    "params": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "[server_name, version, user_modes, channel_modes]."
+    }
+  },
+  "required": [
+    "command",
+    "to",
+    "params"
+  ],
+  "examples": [
+    {
+      "command": "004",
+      "to": "alice",
+      "params": [
+        "chat.example.com",
+        "0.1.0",
+        "o",
+        "imnst+ov"
+      ]
+    }
+  ]
+}

schema/numerics/322.json

@@ -0,0 +1,47 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/322.json",
+  "title": "322 RPL_LIST",
+  "description": "Channel list entry. One per channel in response to LIST. RFC 1459 \u00a76.2.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": {
+      "const": "322"
+    },
+    "to": {
+      "type": "string"
+    },
+    "params": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "[channel, visible_count]."
+    },
+    "body": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "Channel topic."
+    }
+  },
+  "required": [
+    "command",
+    "to",
+    "params"
+  ],
+  "examples": [
+    {
+      "command": "322",
+      "to": "alice",
+      "params": [
+        "#general",
+        "12"
+      ],
+      "body": [
+        "General discussion"
+      ]
+    }
+  ]
+}

schema/numerics/323.json

@@ -0,0 +1,13 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/323.json",
+  "title": "323 RPL_LISTEND",
+  "description": "End of channel list. RFC 1459 §6.2.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "323" },
+    "to": { "type": "string" },
+    "body": { "const": "End of /LIST" }
+  },
+  "required": ["command", "to"]
+}

schema/numerics/332.json

@@ -0,0 +1,47 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/332.json",
+  "title": "332 RPL_TOPIC",
+  "description": "Channel topic (sent on JOIN or TOPIC query). RFC 1459 \u00a76.2.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": {
+      "const": "332"
+    },
+    "to": {
+      "type": "string"
+    },
+    "params": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "[channel]."
+    },
+    "body": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "Topic text."
+    }
+  },
+  "required": [
+    "command",
+    "to",
+    "params",
+    "body"
+  ],
+  "examples": [
+    {
+      "command": "332",
+      "to": "alice",
+      "params": [
+        "#general"
+      ],
+      "body": [
+        "Welcome to the chat"
+      ]
+    }
+  ]
+}

schema/numerics/353.json

@@ -0,0 +1,48 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/353.json",
+  "title": "353 RPL_NAMREPLY",
+  "description": "Channel member list. Sent on JOIN or NAMES query. RFC 1459 \u00a76.2.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": {
+      "const": "353"
+    },
+    "to": {
+      "type": "string"
+    },
+    "params": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "[channel_type, channel]. channel_type: = (public), * (private), @ (secret)."
+    },
+    "body": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "Space-separated list of nicks. Prefixed with @ for ops, + for voiced."
+    }
+  },
+  "required": [
+    "command",
+    "to",
+    "params",
+    "body"
+  ],
+  "examples": [
+    {
+      "command": "353",
+      "to": "alice",
+      "params": [
+        "=",
+        "#general"
+      ],
+      "body": [
+        "@op1 alice bob +voiced1"
+      ]
+    }
+  ]
+}

schema/numerics/366.json

@@ -0,0 +1,18 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/366.json",
+  "title": "366 RPL_ENDOFNAMES",
+  "description": "End of NAMES list. RFC 1459 §6.2.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "366" },
+    "to": { "type": "string" },
+    "params": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "[channel]."
+    },
+    "body": { "const": "End of /NAMES list" }
+  },
+  "required": ["command", "to", "params"]
+}

schema/numerics/372.json

@@ -0,0 +1,36 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/372.json",
+  "title": "372 RPL_MOTD",
+  "description": "MOTD line. One message per line of the MOTD. RFC 2812 \u00a75.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": {
+      "const": "372"
+    },
+    "to": {
+      "type": "string"
+    },
+    "body": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "MOTD line text (prefixed with '- ')."
+    }
+  },
+  "required": [
+    "command",
+    "to",
+    "body"
+  ],
+  "examples": [
+    {
+      "command": "372",
+      "to": "alice",
+      "body": [
+        "- Welcome to our server!"
+      ]
+    }
+  ]
+}

schema/numerics/375.json

@@ -0,0 +1,26 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/375.json",
+  "title": "375 RPL_MOTDSTART",
+  "description": "Start of MOTD. RFC 2812 \u00a75.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": {
+      "const": "375"
+    },
+    "to": {
+      "type": "string"
+    },
+    "body": {
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "description": "Text lines."
+    }
+  },
+  "required": [
+    "command",
+    "to"
+  ]
+}

schema/numerics/376.json

@@ -0,0 +1,13 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/376.json",
+  "title": "376 RPL_ENDOFMOTD",
+  "description": "End of MOTD. RFC 2812 §5.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "376" },
+    "to": { "type": "string" },
+    "body": { "const": "End of /MOTD command" }
+  },
+  "required": ["command", "to"]
+}

schema/numerics/401.json

@@ -0,0 +1,21 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/401.json",
+  "title": "401 ERR_NOSUCHNICK",
+  "description": "No such nick/channel. RFC 1459 §6.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "401" },
+    "to": { "type": "string" },
+    "params": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "[target_nick]."
+    },
+    "body": { "const": "No such nick/channel" }
+  },
+  "required": ["command", "to", "params"],
+  "examples": [
+    { "command": "401", "to": "alice", "params": ["bob"], "body": "No such nick/channel" }
+  ]
+}

schema/numerics/403.json

@@ -0,0 +1,21 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/403.json",
+  "title": "403 ERR_NOSUCHCHANNEL",
+  "description": "No such channel. RFC 1459 §6.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "403" },
+    "to": { "type": "string" },
+    "params": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "[channel_name]."
+    },
+    "body": { "const": "No such channel" }
+  },
+  "required": ["command", "to", "params"],
+  "examples": [
+    { "command": "403", "to": "alice", "params": ["#nonexistent"], "body": "No such channel" }
+  ]
+}

schema/numerics/433.json

@@ -0,0 +1,21 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/433.json",
+  "title": "433 ERR_NICKNAMEINUSE",
+  "description": "Nickname is already in use. RFC 1459 §6.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "433" },
+    "to": { "type": "string" },
+    "params": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "[requested_nick]."
+    },
+    "body": { "const": "Nickname is already in use" }
+  },
+  "required": ["command", "to", "params"],
+  "examples": [
+    { "command": "433", "to": "*", "params": ["alice"], "body": "Nickname is already in use" }
+  ]
+}

schema/numerics/442.json

@@ -0,0 +1,18 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/442.json",
+  "title": "442 ERR_NOTONCHANNEL",
+  "description": "You're not on that channel. RFC 1459 §6.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "442" },
+    "to": { "type": "string" },
+    "params": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "[channel]."
+    },
+    "body": { "const": "You're not on that channel" }
+  },
+  "required": ["command", "to", "params"]
+}

schema/numerics/482.json

@@ -0,0 +1,18 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/numerics/482.json",
+  "title": "482 ERR_CHANOPRIVSNEEDED",
+  "description": "You're not channel operator. RFC 1459 §6.1.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "482" },
+    "to": { "type": "string" },
+    "params": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "[channel]."
+    },
+    "body": { "const": "You're not channel operator" }
+  },
+  "required": ["command", "to", "params"]
+}