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/poll-loop.ts

@@ -366,6 +366,23 @@ async function processQuery(
         if (event.text) {
           dispatchResultText(event.text, routing);
         }
+      } else if (event.type === 'compacted') {
+        // The SDK auto-compacted the conversation. After compaction the
+        // model often drops the learned `<message to="…">` wrapping
+        // discipline (the destinations are still in the system prompt,
+        // but the behavioral pattern is summarized away). Inject a
+        // reminder back into the live query so the next turn re-anchors
+        // on the destination model. Only do this when there's >1
+        // destination — single-destination groups have a fallback that
+        // works without wrapping. See qwibitai/nanoclaw#2325.
+        const destinations = getAllDestinations();
+        if (destinations.length > 1) {
+          const names = destinations.map((d) => d.name).join(', ');
+          query.push(
+            `[system] Context was just compacted. Reminder: you have ${destinations.length} destinations (${names}). ` +
+              `Use <message to="name"> blocks to address them. Bare text goes to the scratchpad fallback only.`,
+          );
+        }
       }
     }
   } finally {
@@ -390,6 +407,9 @@ function handleEvent(event: ProviderEvent, _routing: RoutingContext): void {
     case 'progress':
       log(`Progress: ${event.message}`);
       break;
+    case 'compacted':
+      log(`Compacted: ${event.text}`);
+      break;
   }
 }