feat(fabric): coalesce a split agent turn into ONE message (deterministic)

OpenClaw delivers an agent turn whose blocks are text -> thinking/tool
-> text via multiple inbound deliver() calls (a non-text block is a
delivery boundary), so one turn became N Fabric messages.

Fix: buffer deliver() segments per channel (src/coalesce.ts) and flush
them as ONE postMessage at a deterministic boundary — the finally after
dispatchInboundReplyWithBase() resolves, which provably runs only after
every deliver() of the turn (verified: deliver,deliver -> dispatch
returned -> flush). No hooks, no timers, no idle guessing. The
agent_end hook was rejected: it fires BEFORE deliver(). gateway_stop
flushes any leftover; a long safety timeout is a leak-guard only.
channels.fabric.coalesce=false restores raw per-segment posting.

Verified on local openclaw + Fabric with a fake text/thinking/text
model: single trigger -> exactly one merged message.

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

src/inbound.ts

@@ -5,6 +5,8 @@ import { io, type Socket } from 'socket.io-client';
 import { dispatchInboundReplyWithBase } from 'openclaw/plugin-sdk/inbound-reply-dispatch';
 import type { FabricClient, FabricSession } from './fabric-client.js';
 import type { IdentityRegistry } from './identity.js';
+import { resolveCoalesce } from './accounts.js';
+import { enqueueDelivery, flushFabricForChannel } from './coalesce.js';
 
 // COMPAT NOTE (openclaw v2026.5.7): the inbound path mirrors how bundled
 // channels (nextcloud-talk) drive the kernel:
@@ -301,8 +303,17 @@ export class FabricInbound {
           const text = (payload?.text ?? '').trim();
           this.log.info(`fabric: deliver agent=${agentId} channel=${channelId} len=${text.length}`);
           if (!text || !gt) return;
-          await this.client.postMessage(guild.endpoint, gt, channelId, text, session.user.id);
-          this.log.info(`fabric: posted reply agent=${agentId} channel=${channelId}`);
+          // Buffer segments; the merged message is posted right after
+          // dispatch returns (the deterministic turn boundary, see the
+          // finally below). Disable per channel: channels.fabric.coalesce.
+          await enqueueDelivery({
+            channelId,
+            text,
+            coalesce: resolveCoalesce(this.cfg as never),
+            post: (t) =>
+              this.client.postMessage(guild.endpoint, gt, channelId, t, session.user.id) as Promise<void>,
+            log: (m) => this.log.info(m),
+          });
         },
         onRecordError: (err: unknown) =>
           this.log.warn(`fabric: session record failed agent=${agentId}: ${String(err)}`),
@@ -327,6 +338,12 @@ export class FabricInbound {
       this.log.info(`fabric: dispatch returned agent=${agentId} channel=${channelId}`);
     } catch (err) {
       this.log.warn(`fabric: dispatch failed agent=${agentId} channel=${channelId}: ${String(err)}`);
+    } finally {
+      // Deterministic per-turn boundary: dispatchInboundReplyWithBase only
+      // resolves AFTER every deliver() call of this turn has run, so the
+      // buffer now holds all segments — flush them as ONE Fabric message.
+      // No hooks, no timers, no idle guessing.
+      await flushFabricForChannel(channelId);
     }
   }
 }