docs: module dossier + install/quickstart sync for truthful cutover sprints

- API_CLI_REFERENCE.md, INSTALL_GUIDE.md, quickstart.md, architecture/integrations.md, dev/DEV_ENVIRONMENT_SETUP.md, integrations/LOCAL_SERVICES.md: reflect real-service wiring.
- docs/modules/**: module dossier updates across the modules touched by SPRINT_20260415_001..007 + SPRINT_20260416_003..017 + SPRINT_20260417_018..024 + SPRINT_20260418_025 + SPRINT_20260419_026.
- docs/features/checked/web/**: update feature notes where UI changed.
- docs/qa/feature-checks/runs/web/evidence-presentation-ux/: QA evidence artifacts.
- docs/setup/**, docs/technical/**: align with setup wizard contracts.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/modules/timeline/architecture.md

@@ -124,6 +124,12 @@ TimelineIndexer was consolidated into the Timeline module (Sprint 210, 2026-03-0
 - **Event indexing**: Writes indexed events to PostgreSQL via EfCore (compiled model preserved for migration identity).
 - **Authorization audit**: Provides audit sink for authorization events.
 
+### Ingestion Transport Contract
+
+- Non-testing Timeline hosts must enable at least one real ingestion transport: `Ingestion:Nats:Enabled=true` or `Ingestion:Redis:Enabled=true`.
+- `NullTimelineEventSubscriber` is a testing-only harness and is not registered in live hosts.
+- If both transports are disabled outside `Testing`, startup fails fast with a configuration error instead of exposing an idle ingestion worker.
+
 ### Deployable Services
 
 - **TimelineIndexer WebService** (`StellaOps.TimelineIndexer.WebService`): HTTP API for direct event submission and query.