fix: isolate opencode live status events across threads

[LIU9293]

Summary

• make OpenCode session event filtering robust to sessionID, sessionId, and session_id so concurrent channel runs do not mix live status events
• add watcher-side defensive session filtering before parsing state updates to prevent cross-session bleed-through
• scope dedup keys to channelId:threadId:messageTs and add tests to avoid false duplicate suppression across threads/channels

Testing

• bun test packages/core/test/message-dedup.test.ts packages/core/test/pending-question.test.ts packages/core/test/request-runner.test.ts packages/core/test/status-message.test.ts