chore(docs+devops): cross-module doc sync + sprint archival moves + compose updates

Bundled pre-session doc + ops work:
- docs/modules/**: sync across advisory-ai, airgap, cli, excititor,
  export-center, findings-ledger, notifier, notify, platform, router,
  sbom-service, ui, web (architectural + operational updates)
- docs/features/**: updates to checked excititor vex pipeline,
  developer workspace, quick verify drawer
- docs top-level: README, quickstart, API_CLI_REFERENCE, UI_GUIDE,
  code-of-conduct/TESTING_PRACTICES updates
- docs/qa/feature-checks/: FLOW.md + excititor state update
- docs/implplan/: remaining sprint updates + new Concelier source
  credentials sprint (SPRINT_20260422_003)
- docs-archived/implplan/: 30 sprint archival moves (ElkSharp series,
  misc completed sprints)
- devops/compose: .env + services compose + env example + router gateway
  config updates

File-level granularity preserved.

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

docs/modules/notify/api.md

@@ -25,6 +25,7 @@ All endpoints require `Authorization: Bearer <token>` and `X-Stella-Tenant` head
 - `GET /deliveries` — query delivery ledger; filters: `status`, `channel`, `rule_id`, `from`, `to`. Sorted by `createdUtc` DESC then `id` ASC.
 - `GET /deliveries/{id}` — single delivery with rendered payload hash and attempts.
 - `POST /digests/preview` — preview digest rendering for a tenant/rule set; returns deterministic body/hash without sending.
+- Digest schedule cadence is worker configuration (`Notifier:DigestSchedule`), not an API-managed resource; current digest endpoints administer rendered output or open windows only.
 
 ## Acknowledgements
 - `POST /acks/{token}` — acknowledge an escalation token. Validates DSSE signature, token expiry, and tenant. Returns `200` with cancellation summary.