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/372.json

@@ -2,31 +2,45 @@
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "$id": "https://sneak.berlin/go/neoirc/schema/numerics/372.json",
   "title": "372 RPL_MOTD",
-  "description": "MOTD line. One message per line of the MOTD. RFC 2812 \u00a75.1.",
+  "description": "One line of the message of the day. The server sends one per line, after RPL_MOTDSTART. RFC 2812 §5.1.",
   "$ref": "../message.json",
   "properties": {
     "command": {
-      "const": "372"
+      "const": "RPL_MOTD"
+    },
+    "code": {
+      "const": 372
+    },
+    "from": {
+      "type": "string",
+      "description": "The server name."
     },
     "to": {
-      "type": "string"
+      "type": "string",
+      "description": "The user's nick."
     },
     "body": {
       "type": "array",
       "items": {
         "type": "string"
       },
-      "description": "MOTD line text (prefixed with '- ')."
+      "description": "One string: '- ' and the line.",
+      "minItems": 1,
+      "maxItems": 1
     }
   },
   "required": [
     "command",
+    "code",
+    "from",
     "to",
     "body"
   ],
   "examples": [
     {
-      "command": "372",
+      "command": "RPL_MOTD",
+      "code": 372,
+      "from": "neoirc",
       "to": "alice",
       "body": [
         "- Welcome to our server!"