docs: add v1→v2 action-items analysis + SDK signal probe tool

- docs/v1-vs-v2/: full v1→v2 regression analysis (SUMMARY + 21 per-module
  docs + ACTION-ITEMS rollup with decisions + timezone recreation spec).
- container/agent-runner/scripts/sdk-signal-probe.ts: empirical harness
  used to characterise Claude Agent SDK event/hook/stderr timing for the
  stuck-detection design in item 9.
- src/channels/chat-sdk-bridge.ts: document the conversations Map staleness
  in a code comment; fix deferred to when dynamic group registration lands
  (ACTION-ITEMS item 17).

No runtime behavior change.

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

src/channels/chat-sdk-bridge.ts

@@ -71,6 +71,12 @@ export function createChatSdkBridge(config: ChatSdkBridgeConfig): ChannelAdapter
   let chat: Chat;
   let state: SqliteStateAdapter;
   let setupConfig: ChannelSetup;
+  // NOTE: populated at setup() and updateConversations(), but currently not
+  // read by any inbound handler. When adapter-level gating lands (engage_mode
+  // applied here) or when dynamic group registration is added, this map goes
+  // stale after setup unless updateConversations() is actively called on every
+  // messaging_groups / messaging_group_agents mutation. See ACTION-ITEMS.md
+  // item 17.
   let conversations: Map<string, ConversationConfig>;
   let gatewayAbort: AbortController | null = null;