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/numerics/403.json

@@ -2,39 +2,55 @@
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "$id": "https://sneak.berlin/go/neoirc/schema/numerics/403.json",
   "title": "403 ERR_NOSUCHCHANNEL",
-  "description": "No such channel. RFC 1459 \u00a76.1.",
+  "description": "No channel has that name. A JOIN with a channel name that the server does not allow gets it too. RFC 1459 §6.1.",
   "$ref": "../message.json",
   "properties": {
     "command": {
-      "const": "403"
+      "const": "ERR_NOSUCHCHANNEL"
+    },
+    "code": {
+      "const": 403
+    },
+    "from": {
+      "type": "string",
+      "description": "The server name."
     },
     "to": {
-      "type": "string"
+      "type": "string",
+      "description": "The user's nick."
     },
     "params": {
       "type": "array",
       "items": {
         "type": "string"
       },
-      "description": "[channel_name]."
+      "description": "The channel name.",
+      "minItems": 1,
+      "maxItems": 1
     },
     "body": {
       "type": "array",
       "items": {
         "type": "string"
       },
-      "description": "No such channel",
+      "description": "One string: 'No such channel'.",
+      "minItems": 1,
       "maxItems": 1
     }
   },
   "required": [
     "command",
+    "code",
+    "from",
     "to",
-    "params"
+    "params",
+    "body"
   ],
   "examples": [
     {
-      "command": "403",
+      "command": "ERR_NOSUCHCHANNEL",
+      "code": 403,
+      "from": "neoirc",
       "to": "alice",
       "params": [
         "#nonexistent"