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/PRIVMSG.json

@@ -2,16 +2,16 @@
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "$id": "https://sneak.berlin/go/neoirc/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.",
+  "description": "A message to a channel or a user. A client sends it. The server relays it to every member of the channel, or to the user, and to the sender's own clients. RFC 1459 §4.4.1.",
   "$ref": "../message.json",
   "properties": {
     "command": { "const": "PRIVMSG" },
-    "from": { "type": "string", "description": "Sender nick (set by server on relay)." },
-    "to": { "type": "string", "description": "Target: #channel or nick.", "examples": ["#general", "alice"] },
+    "from": { "type": "string", "description": "The sender's nick. The server sets it." },
+    "to": { "type": "string", "description": "A channel name, which starts with #, or a nick.", "examples": ["#general", "alice"] },
     "body": {
       "type": "array",
       "items": { "type": "string" },
-      "description": "Message lines. One string per line.",
+      "description": "The lines of the message, one string per line.",
       "minItems": 1
     }
   },
@@ -19,6 +19,6 @@
   "examples": [
     { "command": "PRIVMSG", "from": "bob", "to": "#general", "body": ["hello world"] },
     { "command": "PRIVMSG", "from": "bob", "to": "#general", "body": ["line one", "line two"] },
-    { "command": "PRIVMSG", "from": "bob", "to": "alice", "body": ["hey"], "meta": { "sig": "base64...", "alg": "ed25519" } }
+    { "command": "PRIVMSG", "from": "bob", "to": "alice", "body": ["hey"] }
   ]
 }