test(agent-runner): add dispatch, origin metadata, and thread resolution tests

Add 14 tests covering key routing and dispatch flows that previously had
zero direct coverage:

dispatchResultText:
- bare text produces no outbound (scratchpad only)
- unknown destination dropped, valid destination sent
- multiple <message> blocks each produce correct outbound
- internal tags stripped from scratchpad

originAttr / from= metadata:
- chat/task/webhook/system messages include from= when destination matches
- fallback to raw unknown:channel:platform when no match
- from= omitted when routing is null

resolveDestinationThread:
- null thread_id when no prior inbound from destination
- most recent thread_id wins with multiple inbound messages

Also fix merge issue: restore getAllDestinations import removed by our PR
but still needed by #2327's compaction reminder. Fix stale destinations
test assertion from #2328 ("no special wrapping needed" → "Every response
must be wrapped").

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

container/agent-runner/src/poll-loop.ts

@@ -1,4 +1,4 @@
-import { findByName, type DestinationEntry } from './destinations.js';
+import { findByName, getAllDestinations, type DestinationEntry } from './destinations.js';
 import { getPendingMessages, markProcessing, markCompleted, type MessageInRow } from './db/messages-in.js';
 import { writeMessageOut } from './db/messages-out.js';
 import { getInboundDb, touchHeartbeat, clearStaleProcessingAcks } from './db/connection.js';