Observability — Timeline enhancements for gates, decisions, and performance

[DevVig]

Summary
Improve docs/timeline/ to record gate results, adaptation decisions, model selections, and timing, keeping a concise human-readable journal.

Why

• Transparent, auditable process aligned with missions and NFRs

Scope

• Standardize timeline entries and ensure they are written for key actions

Tasks

• Define timeline entry schema and markdown layout (compact summary + links)
• Update orchestrator and gate paths to write entries (create files if missing)
• Add docs/timeline/README.md describing fields and retention policy
• Include elapsed times and run-id for correlation

Acceptance Criteria

• Key actions produce timeline updates with links to artifacts
• Status lines correspond to timeline entries

References

• suggestion.md
• a2a/orchestrator.py, a2a/gate.py, a2a/status.py