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/providers/claude.ts

@@ -329,7 +329,7 @@ export class ClaudeProvider implements AgentProvider {
         } else if (message.type === 'system' && (message as { subtype?: string }).subtype === 'compact_boundary') {
           const meta = (message as { compact_metadata?: { pre_tokens?: number } }).compact_metadata;
           const detail = meta?.pre_tokens ? ` (${meta.pre_tokens.toLocaleString()} tokens compacted)` : '';
-          yield { type: 'result', text: `Context compacted${detail}.` };
+          yield { type: 'compacted', text: `Context compacted${detail}.` };
         } else if (message.type === 'system' && (message as { subtype?: string }).subtype === 'task_notification') {
           const tn = message as { summary?: string };
           yield { type: 'progress', message: tn.summary || 'Task notification' };

container/agent-runner/src/providers/types.ts

@@ -79,4 +79,12 @@ export type ProviderEvent =
    * event (tool call, thinking, partial message, anything) so the
    * poll-loop's idle timer stays honest during long tool runs.
    */
-  | { type: 'activity' };
+  | { type: 'activity' }
+  /**
+   * The provider's underlying SDK auto-compacted the conversation context.
+   * The poll-loop reacts by injecting a destination reminder back into
+   * the live query so the agent doesn't drop `<message to="…">` wrapping
+   * after compaction. Distinct from `result` so it doesn't mark the turn
+   * completed or get dispatched as a chat message. See qwibitai/nanoclaw#2325.
+   */
+  | { type: 'compacted'; text: string };