Make the schema files match the server (closes #218)

Each file in schema/ now describes what the HTTP API on next sends and
accepts. A numeric reply has its name in command and its number in code.
body is always an array of strings. MODE, KICK and JOIN carry their
values in body, and TOPIC needs a non-empty body. PING takes no token,
and its PONG is the HTTP response. A channel name is limited to 63
characters, and the leading # is optional from a client.

PUBKEY.json is deleted, since the server has no such command. The
section of schema/README.md that listed the differences is removed,
and the sentences it made false are corrected.

Model: opus-5-5

schema/commands/PART.json

@@ -2,17 +2,20 @@
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "$id": "https://sneak.berlin/go/neoirc/schema/commands/PART.json",
   "title": "PART",
-  "description": "Leave a channel. C2S: request to leave. S2C: notification that a user left. RFC 1459 §4.2.2.",
+  "description": "Leave a channel. A client sends it to leave. The server sends it to every member of the channel when a user leaves, the leaving user included. RFC 1459 §4.2.2.",
   "$ref": "../message.json",
   "properties": {
     "command": { "const": "PART" },
-    "from": { "type": "string", "description": "Nick that left (S2C)." },
-    "to": { "type": "string", "description": "Channel name.", "pattern": "^#[a-zA-Z0-9_-]+$" },
+    "from": { "type": "string", "description": "The nick that left. The server sets it." },
+    "to": {
+      "type": "string",
+      "description": "The channel name. The server adds the # if a client leaves it out.",
+      "pattern": "^#?[a-zA-Z0-9_-]{1,63}$"
+    },
     "body": {
       "type": "array",
       "items": { "type": "string" },
-      "description": "Optional part reason.",
-      "maxItems": 1
+      "description": "The reason for leaving. A client may send one as the first string. The server always sends one string, which is empty when no reason was given."
     }
   },
   "required": ["command", "to"],