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/message.json

@@ -2,67 +2,55 @@
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "$id": "https://sneak.berlin/go/neoirc/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.).",
+  "description": "Every message in the HTTP API is one JSON object with these fields. Only 'command' is always present.",
   "type": "object",
   "properties": {
     "id": {
       "type": "string",
       "format": "uuid",
-      "description": "Server-assigned message UUID. Present on all server-originated messages."
+      "description": "The message's UUID, which the server assigns. Present on every message the server queues for a client."
     },
     "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"]
+      "description": "An IRC command name, such as PRIVMSG, or the name of a numeric reply, such as RPL_WELCOME. The server reads a client's command in any case and sends it in upper case.",
+      "examples": ["PRIVMSG", "JOIN", "RPL_WELCOME", "ERR_NICKNAMEINUSE"]
+    },
+    "code": {
+      "type": "integer",
+      "minimum": 1,
+      "maximum": 999,
+      "description": "The number of a numeric reply, such as 1 for RPL_WELCOME. Absent on other messages."
     },
     "from": {
       "type": "string",
-      "description": "Source — nick for user messages, server name for server messages. Equivalent to IRC prefix."
+      "description": "The sender's nick, or the server name on a numeric reply or a PONG. The server sets it and ignores it from a client."
     },
     "to": {
       "type": "string",
-      "description": "Target — channel (#name) or nick. Equivalent to first IRC parameter for most commands."
+      "description": "The target: a channel name, such as #general, or a nick. A WALLOPS has * here."
     },
     "params": {
       "type": "array",
       "items": { "type": "string" },
-      "description": "Additional parameters (used primarily by numeric replies). Equivalent to IRC middle parameters."
+      "description": "The message's other parameters, in order. KICK events and many numeric replies have it. The server ignores it from a client."
     },
     "body": {
-      "oneOf": [
-        {
-          "type": "array",
-          "items": { "type": "string" },
-          "description": "Array of strings (one per line for text messages)."
-        },
-        {
-          "type": "object",
-          "description": "Structured data (e.g. PUBKEY key material).",
-          "additionalProperties": true
-        }
-      ],
-      "description": "Message body. MUST be an array or object, never a raw string. Arrays represent lines of text; objects carry structured data. This enables deterministic canonicalization (RFC 8785 JCS) for signing."
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "An array of strings, never a bare string. In a PRIVMSG or NOTICE, each string is one line of text."
     },
     "ts": {
       "type": "string",
       "format": "date-time",
-      "description": "Server-assigned timestamp (ISO 8601). Not present in original IRC; added for HTTP transport."
+      "description": "The time the server stored the message, as an RFC 3339 time in UTC."
     },
     "meta": {
       "type": "object",
-      "description": "Extensible metadata. Used for signatures (meta.sig, meta.alg), hashes (meta.hash), and client extensions.",
+      "description": "An object of extra data. Every message the server queues for a client has meta, which is {} when there is none. The server keeps a client's meta only on a PRIVMSG or NOTICE, and relays it unchanged.",
       "properties": {
-        "sig": {
+        "hashcash": {
           "type": "string",
-          "description": "Base64-encoded cryptographic signature over the canonical message form."
-        },
-        "alg": {
-          "type": "string",
-          "description": "Signature algorithm (e.g. 'ed25519')."
-        },
-        "hash": {
-          "type": "string",
-          "description": "Hash of the canonical message form (e.g. 'sha256:base64...')."
+          "description": "A hashcash stamp. A PRIVMSG to a channel with mode +H needs one."
         }
       },
       "additionalProperties": true