fix(scheduler): make shadow scheduling read-only

[mattebad]

REC-F05 — initialization-free, mutation-free shadow scheduling

Baseline: d150b7861983b09f0d6e1060b2282c85f6694134 (merged PR #6).

Acceptance

• CLI shadow and non-live run leave absent database paths/directories absent; use isolated query-only memory state.
• Existing canonical state opens read-only; service construction/shadow do not seed flow rows, advance occurrences/clocks, claim runs, reserve actions, acquire leases, or start handlers.
• Existing due rows still yield candidate diagnostics with no run ID.
• Read-only state explicitly rejects mutation and real scheduler execution.
• Real controls and execution retain explicit disabled-flow initialization and persisted gates. Includes the retained pnsctl real pulse caller cutover.
• Escaped SQLite URI paths address the exact file; failed setup closes handles on Windows.

Verification (Windows, isolated Python 3.12)

• python -m unittest tests.test_automation_service_canonical_authority tests.test_automation_service_cli tests.test_automation_service_scheduler_canonical tests.test_pnsctl_scheduler_pulse — 48 passed.
• python scripts/check.py — 298 passed.
• Existing affected CI selection — 114 passed (same modules retained in offline.yml).
• python -m compileall -q automation_service safe_action_core scripts tasks tools — passed.
• git diff --cached --check and git diff --check d150b7861983b09f0d6e1060b2282c85f6694134...HEAD — passed.
• Disposable public-CLI/API smoke: absent shadow path remains absent; mutation and real pulse denied on isolated read-only state; literal # filename opens exact DB.

CI adds the focused tests to both Windows and Ubuntu jobs; hosted results remain the merge gate. Offline green is not native/scheduler/production acceptance. No device, native observation, production-state mutation, registration, enablement, or protected evidence changes. No merge requested.