feat: Implement Scheduler Worker Options and Planner Loop

- Added `SchedulerWorkerOptions` class to encapsulate configuration for the scheduler worker.
- Introduced `PlannerBackgroundService` to manage the planner loop, fetching and processing planning runs.
- Created `PlannerExecutionService` to handle the execution logic for planning runs, including impact targeting and run persistence.
- Developed `PlannerExecutionResult` and `PlannerExecutionStatus` to standardize execution outcomes.
- Implemented validation logic within `SchedulerWorkerOptions` to ensure proper configuration.
- Added documentation for the planner loop and impact targeting features.
- Established health check endpoints and authentication mechanisms for the Signals service.
- Created unit tests for the Signals API to ensure proper functionality and response handling.
- Configured options for authority integration and fallback authentication methods.

src/StellaOps.Scheduler.WebService/TASKS.md

@@ -1,8 +1,8 @@
-# Scheduler WebService Task Board (Sprint 16)
-
-| ID | Status | Owner(s) | Depends on | Description | Exit Criteria |
-|----|--------|----------|------------|-------------|---------------|
-| SCHED-WEB-16-101 | DOING (2025-10-19) | Scheduler WebService Guild | SCHED-MODELS-16-101 | Bootstrap Minimal API host with Authority OpTok + DPoP, health endpoints, plug-in discovery per architecture §§1–2. | Service boots with config validation; `/healthz`/`/readyz` pass; restart-only plug-ins enforced. |
+# Scheduler WebService Task Board (Sprint 16)
+
+| ID | Status | Owner(s) | Depends on | Description | Exit Criteria |
+|----|--------|----------|------------|-------------|---------------|
+| SCHED-WEB-16-101 | DONE (2025-10-27) | Scheduler WebService Guild | SCHED-MODELS-16-101 | Bootstrap Minimal API host with Authority OpTok + DPoP, health endpoints, plug-in discovery per architecture §§1–2. | Service boots with config validation; `/healthz`/`/readyz` pass; restart-only plug-ins enforced. |
 | SCHED-WEB-16-102 | DONE (2025-10-26) | Scheduler WebService Guild | SCHED-WEB-16-101 | Implement schedules CRUD (tenant-scoped) with cron validation, pause/resume, audit logging. | CRUD operations tested; invalid cron inputs rejected; audit entries persisted. |
 | SCHED-WEB-16-103 | DONE (2025-10-26) | Scheduler WebService Guild | SCHED-WEB-16-102 | Runs API (list/detail/cancel), ad-hoc run POST, and impact preview endpoints. | Integration tests cover run lifecycle; preview returns counts/sample; cancellation honoured. |
 | SCHED-WEB-16-104 | DONE (2025-10-27) | Scheduler WebService Guild | SCHED-QUEUE-16-401, SCHED-STORAGE-16-201 | Webhook endpoints for Feeder/Vexer exports with mTLS/HMAC validation and rate limiting. | Webhooks validated via tests; invalid signatures rejected; rate limits documented. |
@@ -42,5 +42,4 @@
 | SCHED-VULN-29-002 | TODO | Scheduler WebService Guild, Observability Guild | SCHED-VULN-29-001 | Provide projector lag metrics endpoint and webhook notifications for backlog breaches consumed by DevOps dashboards. | Lag metrics exposed; webhook events triggered on thresholds; docs updated. |
 
 ## Notes
-- 2025-10-19: SCHED-MODELS-16-101 (schemas/DTOs) is DONE, so API contracts for schedules/runs are ready to consume.
-- Next steps for SCHED-WEB-16-101: create Minimal API host project scaffold, wire Authority OpTok + DPoP authentication via existing DI helpers, expose `/healthz` + `/readyz`, and load restart-only plugins per architecture §§1–2. Capture configuration validation and log shape aligned with Scheduler platform guidance before moving to CRUD implementation.
+- 2025-10-27: Minimal API host now wires Authority, health endpoints, and restart-only plug-in discovery per architecture §§1–2.