implemented unified operational timeline. situational awareness 'what changed before it broke?'

CHANGELOG.md

@@ -9,7 +9,13 @@ Versions follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
-### In Progress — Phase 3A (Environment model + deployment tracking)
+### In Progress — Phase 3B (Unified Operational Timeline)
+- `GET /api/v1/repos/:owner/:repo/timeline` — merges commits, pipeline runs, and deployments into a single chronological feed
+- `RepoTimelinePage` at `/repos/:owner/:repo/timeline` — vertical event feed with type filter tabs
+- Sidebar "Timeline" nav item between Environments and Settings
+- Event types: commit (SHA, message, author), run (status, ref, duration), deployment (env, status, SHA)
+
+### Completed — Phase 3A (Environment model + deployment tracking)
 - `Environment` model per repo (name, URL, protection rules)
 - `Deployment` model (sha, ref, status, triggered_by, run_id link)
 - Full CRUD API for environments