address review: add thread resolution test, log catch, remove stray comment

- Add integration test for per-destination thread_id resolution: seeds two
  destinations with different thread IDs, verifies each outbound message
  carries the correct thread_id (not a global one from the batch routing).
- Add log line in resolveDestinationThread catch block for debuggability.
- Remove stray "(ensurePreCompactHook is defined after the main function.)"
  comment from group-init.ts.

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

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

@@ -478,8 +478,8 @@ function resolveDestinationThread(
       )
       .get(channelType, platformId) as { thread_id: string | null; id: string } | undefined;
     if (row) return { threadId: row.thread_id, inReplyTo: row.id };
-  } catch {
-    // Fall through — DB may not have these columns on older sessions
+  } catch (err) {
+    log(`resolveDestinationThread error: ${err instanceof Error ? err.message : String(err)}`);
   }
   return null;
 }