Stability checkpoint stable-v1.0.24 (UI) — Phase 4.2 wave continued: 33 new UI tests across 3 core services (ActivityService 12, DeepLinkService 13, FeatureFlagService 8). Activity timeline contract pinned (newest-first ordering, 200-event cap, monotonic ids). DeepLink URI builders tested (vscode/idea/docker-desktop). FeatureFlag hidden-by-default contract pinned + isAvailable reactivity. Cumulative UI Phase 4.2 across v1.0.23-24: 54 new UI tests. Post-merge main pipeline #380 SUCCESS.