chore: remove superseded schema files

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

schema/commands/PRIVMSG.json

@@ -1,29 +0,0 @@
-{
-  "$schema": "https://json-schema.org/draft/2020-12/schema",
-  "$id": "https://git.eeqj.de/sneak/chat/schema/commands/PRIVMSG.json",
-  "title": "PRIVMSG",
-  "description": "Send a message to a channel or user. C2S: client sends to server. S2C: server relays to recipients. RFC 1459 §4.4.1.",
-  "$ref": "../message.json",
-  "properties": {
-    "command": { "const": "PRIVMSG" },
-    "from": {
-      "type": "string",
-      "description": "Sender nick (set by server on S2C relay)."
-    },
-    "to": {
-      "type": "string",
-      "description": "Target: #channel or nick.",
-      "examples": ["#general", "alice"]
-    },
-    "body": {
-      "type": "string",
-      "description": "Message text.",
-      "minLength": 1
-    }
-  },
-  "required": ["command", "to", "body"],
-  "examples": [
-    { "command": "PRIVMSG", "from": "bob", "to": "#general", "body": "hello world" },
-    { "command": "PRIVMSG", "from": "bob", "to": "alice", "body": "hey" }
-  ]
-}