Gateway-Edge Hybrid Rules Engine: settings, motion score, decision-core wiring

[dmichael-fastly]

Summary

Implements Sections A-D of the Gateway-Edge Hybrid Rules Engine spec (docs/superpowers/specs/2026-07-27-rules-engine-trigger-design.md), per the plan at docs/superpowers/plans/2026-07-27-rules-engine-gateway-edge-plan.md:

• Edge (Rust): new garden_state settings (motion_sensitivity, human_auto_disarm_minutes, rain_suppression_enabled, auto_disarm_until) exposed on GET /api/state and writable via a new admin-gated POST /api/settings.
• Pi camera daemon: exposes the per-camera motion score it already computes over a new GET /motion_score?device=<did> route.
• Pi gateway: extends the existing local_precheck/resolve_motion fail-closed decision core with an auto-disarm window, a rain-suppression toggle, and a camera-motion veto; sources the evidence JPEG from camera_daemon when the radar node has none of its own (fixing a real gap where a camera-less node could never spray via this path).

Explicitly out of scope (per the spec's own sequencing): human/ML detection (Section E, open research item) and the real ESP32 firmware rework to gate the spray on this round-trip (Section F, follow-up plan).

Test plan

• cargo test (118 passed) + make build-check (wasm32-wasip1 compiles)
• python3 -m pytest -q (520 passed, 5 pre-existing skips)
• make ci green (gen-check, css-check, build-check, Rust + Python tests, gitleaks)
• Updated the pinned safety-invariant suite (tests/test_safety_properties.py) and the simulator e2e harness (tests/test_sim_e2e.py) for the new Gateway/local_precheck/resolve_motion signatures — both found mid-implementation, not in the original plan.