docs: phase-4 deploy + smoke test complete, mission done

All smoke tests pass: web HTTP 200, API healthy, dashboard renders
with all widgets, auth working. Fixed root route redirect that
prevented dashboard from rendering at /.

Mission: mosaic-stack-go-live-mvp-20260222 — 4/4 milestones complete.

Issue: #463

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/scratchpads/mosaic-stack-go-live-mvp-20260222.md

@@ -74,6 +74,28 @@ Estimated total: ~50K tokens
 | ------- | ---------- | --------- | ---------- | ------------------------------------------------------ |
 | S2 cont | 2026-02-23 | phase-3   | 3/3        | COMPLETE — PR #462 merged (458cac7), issue #461 closed |
 
+### 2026-02-23: Phase-4 Completion Summary
+
+- 3/3 tasks done (MS-P4-001 through MS-P4-003)
+- Built stack-api and stack-web Docker images locally, pushed to git.mosaicstack.dev/mosaic/ registry
+- Fixed root route redirect: removed app/page.tsx that was intercepting / and redirecting to /tasks
+- Coolify service stop+start cycle required (restart alone caused flaky proxy routing)
+- Proxy routing note: Traefik route propagation takes ~5min after service restart; multiple rapid cycles cause intermittent 504s
+- Smoke test results: web HTTP 200 (0.19s), API health HTTP 200 (0.10s), dashboard API HTTP 401 (auth required)
+- Dashboard verified in browser: all 6 widgets rendering, auth working (User: Jarvis), dark/light theme toggle
+- All quality gates green: lint 8/8, typecheck 7/7, test 8/8
+- Screenshot saved: docs/scratchpads/smoke-test-dashboard.png
+
+| Session | Date       | Milestone | Tasks Done | Outcome                 |
+| ------- | ---------- | --------- | ---------- | ----------------------- |
+| S3      | 2026-02-23 | phase-4   | 3/3        | COMPLETE — mission done |
+
+### Mission Summary
+
+- 4 milestones, 16 tasks, 4 PRs (#458, #460, #462, + phase-4 PR), 4 issues (#457, #459, #461, #463)
+- Success criteria met: dashboard at mosaic.woltje.com, task ingestion API, agent cycle visibility, deployed + smoke-tested
+- Known infra issue: Coolify proxy routing is flaky after rapid restart cycles; needs 5min stabilization
+
 ## Open Questions
 
 ## Corrections