feat(plugin): sync OpenClaw slash-command catalog to Fabric

- command-sync.ts: buildFabricCommandSpecs(cfg) reads OpenClaw native
  command specs via openclaw/plugin-sdk/native-command-registry
  (listNativeCommandSpecsForConfig + findCommandByNativeName), resolves
  dynamic arg choices to a static snapshot (resolveCommandArgChoices) —
  same data Discord registers as slash commands.
- syncFabricCommands(): on gateway_start, after inbound starts, PUT the
  catalog to each connected guild (FabricClient.syncCommands ->
  PUT /api/commands; idempotent, one per guild).
- Fabric stays a TEXT-command surface (no nativeCommands capability):
  execution still flows as a /<cmd> message into OpenClaw's command
  system; this catalog only drives frontend autocomplete.

Verified: 41 specs built (args/choices incl. dynamic), synced to
test-guild1, GET /api/commands round-trips count=41.

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

dist/fabric/src/fabric-client.js

@@ -71,6 +71,12 @@ export class FabricClient {
     leaveChannel(guildEndpoint, guildToken, channelId) {
         return this.post(`${guildEndpoint}/api/channels/${channelId}/leave`, {}, guildToken);
     }
+    // Register the OpenClaw slash-command catalog with this guild (idempotent
+    // full replace). The frontend GETs it for `/` autocomplete; execution
+    // still flows as a normal /<cmd> message into OpenClaw's command system.
+    syncCommands(guildEndpoint, guildToken, commands) {
+        return this.req('PUT', `${guildEndpoint}/api/commands`, guildToken, { commands });
+    }
     // [{ userId, bypass }] — bypass is true only for discuss/work bypass-list
     channelMembers(guildEndpoint, guildToken, channelId) {
         return this.req('GET', `${guildEndpoint}/api/channels/${channelId}/members`, guildToken);