feat(plugin): fabric-canvas tool; fabric-register env=AGENT_ID only

- bin/fabric-register.mjs: only AGENT_ID is read from the environment;
  --api-key is flag-only (no FABRIC_API_KEY); dropped FABRIC_CENTER_API_BASE
  / FABRIC_IDENTITY_FILE / OPENCLAW_PATH env fallbacks (flags + sensible
  defaults; --center still falls back to openclaw.json).
- New fabric-canvas tool (one tool, four actions): read / share / update /
  close the channel's single pinned canvas. Backed by FabricClient
  get/share/update/removeCanvas (GET/PUT/PATCH/DELETE; empty 2xx body ->
  null). update/close are sharer-only server-side.
- README updated.

Verified: client-level smoke against the running guild —
read(empty→null) → share(v1) → read → update(v2) → close(→null) all pass.

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

src/tools.ts

@@ -120,4 +120,83 @@ export function registerFabricTools(
       return { ok: true, closed: true };
     },
   }));
+
+  // fabric-canvas: share / update / read / close the channel's single
+  // pinned canvas document (one tool, four actions). update/close are
+  // sharer-only server-side (the guild returns 403 otherwise).
+  api.registerTool((ctx: Ctx) => ({
+    name: 'fabric-canvas',
+    description:
+      "Manage a channel's pinned canvas document. action: " +
+      "read (current canvas or null) | share (create/replace; you become " +
+      'the sharer) | update (edit in place; sharer only) | close (remove; ' +
+      'sharer only).',
+    parameters: {
+      type: 'object',
+      additionalProperties: false,
+      required: ['action', 'guildNodeId', 'channelId'],
+      properties: {
+        action: { type: 'string', enum: ['read', 'share', 'update', 'close'] },
+        guildNodeId: { type: 'string' },
+        channelId: { type: 'string' },
+        title: { type: 'string', description: 'share: required; update: optional' },
+        format: {
+          type: 'string',
+          enum: ['md', 'html', 'text'],
+          description: 'share: required; update: optional',
+        },
+        source: {
+          type: 'string',
+          description: 'document body. share: required; update: optional',
+        },
+      },
+    },
+    execute: async (p: {
+      action: 'read' | 'share' | 'update' | 'close';
+      guildNodeId: string;
+      channelId: string;
+      title?: string;
+      format?: 'md' | 'html' | 'text';
+      source?: string;
+    }) => {
+      const agentId = ctx.agentId;
+      if (!agentId) return { ok: false, error: 'no agent context' };
+      const { guild, token } = await ctxGuild(agentId, p.guildNodeId);
+      const ep = guild.endpoint;
+      switch (p.action) {
+        case 'read': {
+          const canvas = await client.getCanvas(ep, token, p.channelId);
+          return { ok: true, canvas };
+        }
+        case 'share': {
+          if (!p.title || !p.format || p.source === undefined) {
+            return { ok: false, error: 'share requires title, format, and source' };
+          }
+          const canvas = await client.shareCanvas(ep, token, p.channelId, {
+            title: p.title,
+            format: p.format,
+            source: p.source,
+          });
+          return { ok: true, canvas };
+        }
+        case 'update': {
+          const body: Partial<{ title: string; format: 'md' | 'html' | 'text'; source: string }> = {};
+          if (p.title !== undefined) body.title = p.title;
+          if (p.format !== undefined) body.format = p.format;
+          if (p.source !== undefined) body.source = p.source;
+          if (Object.keys(body).length === 0) {
+            return { ok: false, error: 'update needs at least one of title/format/source' };
+          }
+          const canvas = await client.updateCanvas(ep, token, p.channelId, body);
+          return { ok: true, canvas };
+        }
+        case 'close': {
+          await client.removeCanvas(ep, token, p.channelId);
+          return { ok: true, removed: true };
+        }
+        default:
+          return { ok: false, error: `unknown action ${String(p.action)}` };
+      }
+    },
+  }));
 }