chore: remove superseded schema files

Remove schema/commands/ and schema/message.json, replaced by
the new schema/{c2s,s2c,s2s}/*.schema.json structure.

schema/message.json

@@ -1,46 +0,0 @@
-{
-  "$schema": "https://json-schema.org/draft/2020-12/schema",
-  "$id": "https://git.eeqj.de/sneak/chat/schema/message.json",
-  "title": "IRC Message Envelope",
-  "description": "Base envelope for all messages. Mirrors IRC wire format (RFC 1459/2812) encoded as JSON over HTTP. The 'command' field carries either an IRC command name (PRIVMSG, JOIN, etc.) or a three-digit numeric reply code (001, 353, 433, etc.).",
-  "type": "object",
-  "properties": {
-    "id": {
-      "type": "integer",
-      "description": "Server-assigned message ID, monotonically increasing. Present on all server-originated messages."
-    },
-    "command": {
-      "type": "string",
-      "description": "IRC command name (PRIVMSG, JOIN, NICK, etc.) or three-digit numeric reply code (001, 353, 433, etc.).",
-      "examples": ["PRIVMSG", "JOIN", "001", "353", "433"]
-    },
-    "from": {
-      "type": "string",
-      "description": "Source — nick for user messages, server name for server messages. Equivalent to IRC prefix."
-    },
-    "to": {
-      "type": "string",
-      "description": "Target — channel (#name) or nick. Equivalent to first IRC parameter for most commands."
-    },
-    "params": {
-      "type": "array",
-      "items": { "type": "string" },
-      "description": "Additional parameters (used primarily by numeric replies). Equivalent to IRC middle parameters."
-    },
-    "body": {
-      "type": "string",
-      "description": "Message body / trailing parameter. Equivalent to IRC trailing parameter (after the colon)."
-    },
-    "ts": {
-      "type": "string",
-      "format": "date-time",
-      "description": "Server-assigned timestamp (ISO 8601). Not present in original IRC; added for HTTP transport."
-    },
-    "meta": {
-      "type": "object",
-      "description": "Extensible metadata (signatures, rich content hints, etc.). Not present in original IRC.",
-      "additionalProperties": true
-    }
-  },
-  "required": ["command"]
-}