feat: live Feishu employee collaboration updates

[0YHR0]

Summary

• Separately opt-in live coordinated employee notifications: started work, pinned incoming deliveries, provisional results and failures.
• Persist only references in the same Run transaction, with stable delivery IDs, rollback safety and deduplication; no schema change.
• Project exact pinned coordinator evidence with task/run/subtask/tenant checks. Never send raw inputs, prompts, memory or provider error bodies.
• Business excerpts require another explicit opt-in; bounded credential-pattern filtering is not semantic confidentiality. Pace outbound delivery and keep it independent of execution.
• Preserve existing task/approval cards and document English/Chinese setup.

Validation

• Full non-PostgreSQL regression suite passed.
• 50 targeted notification/configuration/projection tests passed.
• 23 real PostgreSQL tests passed on an isolated test database, including atomic rollback, repeat-save dedup and real-store delivery after task completion.
• Ruff and diff checks pass.

Live qualification completed in the private deployment using four separately published real DeepSeek employees. Eight collaboration messages and one task-completion message were acknowledged by the real Feishu send API, each on its first attempt. Pinned incoming deliveries were also re-projected from the database successfully. Public collaboration sync remains disabled. No credential or deployment address is included in the repository. See docs/qualification/feishu-collaboration.md for scope and limits.