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>

dist/fabric/src/fabric-client.js

@@ -21,6 +21,24 @@ export class FabricClient {
         }
         return (await res.json());
     }
+    // Generic JSON request (GET/PUT/PATCH/DELETE). Empty 2xx body -> null
+    // (Fabric returns an empty body when a channel has no canvas).
+    async req(method, url, auth, body) {
+        const res = await fetch(url, {
+            method,
+            headers: {
+                ...(body !== undefined ? { 'content-type': 'application/json' } : {}),
+                ...(auth ? { authorization: `Bearer ${auth}` } : {}),
+            },
+            body: body !== undefined ? JSON.stringify(body) : undefined,
+        });
+        if (!res.ok) {
+            const text = await res.text().catch(() => '');
+            throw new Error(`${method} ${url} -> ${res.status} ${text}`);
+        }
+        const text = await res.text();
+        return (text ? JSON.parse(text) : null);
+    }
     // Exchange an agent API key for a Fabric user session (+ guild tokens).
     agentLogin(apiKey) {
         return this.post(`${this.centerApiBase}/auth/agent/login`, { apiKey });
@@ -50,4 +68,24 @@ export class FabricClient {
     joinChannel(guildEndpoint, guildToken, channelId) {
         return this.post(`${guildEndpoint}/api/channels/${channelId}/join`, {}, guildToken);
     }
+    // ---- channel canvas (one pinned doc per channel) ----
+    canvasUrl(endpoint, channelId) {
+        return `${endpoint}/api/channels/${channelId}/canvas`;
+    }
+    // null when the channel has no canvas
+    getCanvas(endpoint, token, channelId) {
+        return this.req('GET', this.canvasUrl(endpoint, channelId), token);
+    }
+    // share / replace (caller becomes the sharer)
+    shareCanvas(endpoint, token, channelId, body) {
+        return this.req('PUT', this.canvasUrl(endpoint, channelId), token, body);
+    }
+    // update in place (original sharer only — else the guild returns 403)
+    updateCanvas(endpoint, token, channelId, body) {
+        return this.req('PATCH', this.canvasUrl(endpoint, channelId), token, body);
+    }
+    // remove ("close") the canvas (original sharer only)
+    removeCanvas(endpoint, token, channelId) {
+        return this.req('DELETE', this.canvasUrl(endpoint, channelId), token);
+    }
 }

dist/fabric/src/tools.js

@@ -89,4 +89,78 @@ export function registerFabricTools(api, client, identity) {
             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) => ({
+        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) => {
+            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 = {};
+                    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)}` };
+            }
+        },
+    }));
 }