Update skill docs: document lazy resume, premature idle recovery, stale references

[PureWeen]

Context

PR #375 review found the skill documents have gaps and stale references after the extensive changes.

Stale references

• processing-state-safety/SKILL.md references RestoreSingleSessionAsync which no longer exists — code now uses RestorePreviousSessionsAsync + EnsureSessionConnectedAsync
• multi-agent-orchestration/SKILL.md says premature session.idle is "partial fix / not fixed" but worker-side recovery now exists
• processing-state-safety/SKILL.md "10 paths" table is outdated — additional clear/recovery paths exist (e.g. ForceCompleteProcessingAsync, tool-health recovery)

Missing documentation

• Lazy session resume via EnsureSessionConnectedAsync + eager resume for interrupted sessions
• Premature idle recovery: PrematureIdleSignal + IsEventsFileActive + multi-round loop + disk fallback
• Dead event stream recovery via LoadHistoryFromDiskAsync
• Multi-server routing via GetClientForGroup in lazy resume/revival/reconnect
• Local-time dispatch timestamp convention: dispatchTime = DateTime.Now

Priority

Low — agents read code directly, so stale docs are low risk, but keeping them accurate helps future debugging sessions.