feat(guild): slash-command registry (sync + list API)

Guild-global slash-command catalog (one row per node guild). The
OpenClaw plugin PUTs the native-command specs (same data Discord
registers as slash commands); the frontend GETs it for / autocomplete.

- GuildCommand entity (guild_id unique, commands json, updatedAt)
- PUT /api/commands  -> idempotent full replace (any authed agent/user)
- GET /api/commands  -> { commands, updatedAt } (authed)
- stored verbatim (NativeCommandSpec-shaped); execution path unchanged:
  a /<cmd> message is delivered as a normal message -> plugin ->
  OpenClaw command system (only /no-reply, /force-proceed stay
  server-intercepted).

Verified: PUT->{ok,count}, GET round-trips args/choices, no-auth->401.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/entities/guild-command.entity.ts

@@ -0,0 +1,25 @@
+import { Column, Entity, Index, PrimaryGeneratedColumn, UpdateDateColumn } from 'typeorm';
+
+// Guild-global slash-command catalog. One row per guild (this node's
+// FABRIC_BACKEND_GUILD_NODE_ID). The OpenClaw plugin PUTs the OpenClaw
+// native-command specs here (the same data Discord registers as slash
+// commands); the frontend GETs it to drive `/` autocomplete. The guild
+// node stores the catalog opaquely — it does not interpret command bodies.
+@Entity('guild_commands')
+export class GuildCommand {
+  @PrimaryGeneratedColumn('uuid')
+  id!: string;
+
+  @Index({ unique: true })
+  @Column({ name: 'guild_id', type: 'varchar', length: 80 })
+  guildId!: string;
+
+  // NativeCommandSpec[]-shaped (name, nativeName, description, acceptsArgs,
+  // args[{name,description,type,required,choices:[{value,label}],
+  // captureRemaining,preferAutocomplete}], argsParsing). Stored verbatim.
+  @Column({ type: 'json' })
+  commands!: unknown[];
+
+  @UpdateDateColumn()
+  updatedAt!: Date;
+}