feat(poll-loop): inject destination reminder after SDK auto-compaction

Closes qwibitai/nanoclaw#2325.

When the Claude Code SDK auto-compacts the conversation context, the
compaction summary tends to drop the agent's learned <message to="…">
wrapping discipline. The destinations table is still populated and the
system prompt still lists them, but the behavioral pattern degrades —
A2A sends and multi-channel routing silently revert to bare-text or
single-channel delivery for the rest of the session, until the next
/clear.

Three small changes wire a reminder back into the live query when this
fires:

- New `compacted` event on ProviderEvent. Distinct from `result` so it
  doesn't mark the turn completed or get dispatched as a chat message
  (which is also why "Context compacted (N tokens compacted)." stops
  appearing as noise in user-facing chats — it was a side-effect of
  reusing the result event path).
- ClaudeProvider yields `compacted` instead of `result` for the SDK's
  compact_boundary system event.
- Poll-loop's event handler reacts by pushing a system-tagged reminder
  back into the active query when there are >1 destinations. Single-
  destination groups skip the push since they have a fallback that
  works without wrapping.

Tests cover both branches (multi-destination → reminder fires;
single-destination → no reminder) using a CompactingProvider that
emits the new event mid-stream.

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

container/agent-runner/src/integration.test.ts

@@ -91,8 +91,116 @@ describe('poll loop integration', () => {
 
     await loopPromise.catch(() => {});
   });
+
+  it('should inject destination reminder after a compacted event', async () => {
+    // Two destinations — required for the reminder to fire (single-destination
+    // groups have a fallback path that works without <message to="…"> wrapping).
+    getInboundDb()
+      .prepare(
+        `INSERT INTO destinations (name, display_name, type, channel_type, platform_id, agent_group_id)
+         VALUES ('discord-second', 'Discord Second', 'channel', 'discord', 'chan-2', NULL)`,
+      )
+      .run();
+
+    insertMessage('m1', { sender: 'Alice', text: 'First message' }, { platformId: 'chan-1', channelType: 'discord' });
+
+    const provider = new CompactingProvider();
+    const controller = new AbortController();
+    const loopPromise = runPollLoopWithTimeout(provider as unknown as MockProvider, controller.signal, 2500);
+
+    await waitFor(() => getUndeliveredMessages().length > 0, 2500);
+    controller.abort();
+
+    expect(provider.pushes.length).toBeGreaterThanOrEqual(1);
+    const reminder = provider.pushes.find((p) => p.includes('Context was just compacted'));
+    expect(reminder).toBeDefined();
+    expect(reminder).toContain('2 destinations');
+    expect(reminder).toContain('discord-test');
+    expect(reminder).toContain('discord-second');
+    expect(reminder).toContain('<message to="name">');
+
+    await loopPromise.catch(() => {});
+  });
+
+  it('should NOT inject destination reminder with a single destination', async () => {
+    insertMessage('m1', { sender: 'Alice', text: 'First message' }, { platformId: 'chan-1', channelType: 'discord' });
+
+    const provider = new CompactingProvider();
+    const controller = new AbortController();
+    const loopPromise = runPollLoopWithTimeout(provider as unknown as MockProvider, controller.signal, 2500);
+
+    await waitFor(() => getUndeliveredMessages().length > 0, 2500);
+    controller.abort();
+
+    // Only the original prompt push (if any) — no reminder, since beforeEach
+    // seeds exactly one destination.
+    const reminders = provider.pushes.filter((p) => p.includes('Context was just compacted'));
+    expect(reminders).toHaveLength(0);
+
+    await loopPromise.catch(() => {});
+  });
 });
 
+/**
+ * Provider that emits a single compacted event mid-stream, then returns a
+ * result. Captures every push() call so tests can assert on the injected
+ * reminder content.
+ */
+class CompactingProvider {
+  readonly supportsNativeSlashCommands = false;
+  readonly pushes: string[] = [];
+
+  isSessionInvalid(): boolean {
+    return false;
+  }
+
+  query(_input: { prompt: string; cwd: string }) {
+    const pushes = this.pushes;
+    let ended = false;
+    let aborted = false;
+    let resolveWaiter: (() => void) | null = null;
+
+    async function* events() {
+      yield { type: 'activity' as const };
+      yield { type: 'init' as const, continuation: 'compaction-test-session' };
+      yield { type: 'activity' as const };
+      yield { type: 'compacted' as const, text: 'Context compacted (50,000 tokens compacted).' };
+
+      // Wait for poll-loop to push the reminder (or end / abort)
+      await new Promise<void>((resolve) => {
+        resolveWaiter = resolve;
+        // Belt-and-braces: don't hang forever if the reminder never arrives
+        setTimeout(resolve, 200);
+      });
+
+      yield { type: 'activity' as const };
+      yield { type: 'result' as const, text: '<message to="discord-test">ack</message>' };
+      while (!ended && !aborted) {
+        await new Promise<void>((resolve) => {
+          resolveWaiter = resolve;
+          setTimeout(resolve, 50);
+        });
+      }
+    }
+
+    return {
+      push(message: string) {
+        pushes.push(message);
+        resolveWaiter?.();
+      },
+      end() {
+        ended = true;
+        resolveWaiter?.();
+      },
+      abort() {
+        aborted = true;
+        resolveWaiter?.();
+      },
+      events: events(),
+    };
+  }
+}
+
 // Helper: run poll loop until aborted or timeout
 async function runPollLoopWithTimeout(provider: MockProvider, signal: AbortSignal, timeoutMs: number): Promise<void> {
   return Promise.race([