fix(vehicle): align navigation_gps_request order default across transports

[Bre77]

Intent

Align navigation_gps_request's order parameter across cloud (REST) and BLE transports per captain's ruling (2026-07-20): default an omitted order to 0 on both paths, rather than cloud omitting the field entirely while BLE required an int. Made order: int = 0 in both VehicleFleet.navigation_gps_request (fleet.py) and Commands.navigation_gps_request (commands.py). Verified 0 = REMOTE_NAV_TRIP_ORDER_UNKNOWN is a defined, valid proto enum value (proto/car_server.proto) safe on both transports' signed-command wire path - not a placeholder hack. Added cross-transport parity tests (tests/test_cross_transport_parity.py) asserting omitted order -> 0 on both cloud JSON payload and BLE protobuf message, and explicit order passes through unchanged. Updated AGENTS.md's cross-transport-parity note marking this divergence as resolved (previously listed as an open divergence pending decision). Full test suite, ruff, and pyright all pass.

What Changed

• VehicleFleet.navigation_gps_request (fleet.py) and Commands.navigation_gps_request (commands.py) now both default order: int = 0 (REMOTE_NAV_TRIP_ORDER_UNKNOWN) when the caller omits it, replacing the prior mismatch where cloud omitted the field entirely (order: int | None = None) while BLE required a caller-supplied int.
• Updated both methods' docstrings to note the new default, and updated AGENTS.md's cross-transport-parity note to mark this divergence resolved (was previously listed as open/pending decision).
• Added NavigationGpsRequestParityTests to tests/test_cross_transport_parity.py asserting an omitted order resolves to 0 on both the cloud JSON payload and the BLE protobuf message, and that an explicit order still passes through unchanged.
• Updated docs/bluetooth_vehicles.md and docs/fleet_api_signed_commands.md to reflect the new default; uv.lock updated incidentally.

Risk Assessment

✅ Low: Small, well-bounded signature change (order: int = 0 on both transports) verified against the proto enum, with cross-transport parity tests covering both the default and explicit-order paths, and no other call sites depend on the old None/required signature.

Testing

Ran the new and full test suites (364 passed) and manually exercised VehicleFleet.navigation_gps_request in a live Python REPL to confirm the actual outgoing REST JSON payload now includes order: 0 when omitted (previously the field would be absent), matching the BLE side's protobuf default verified by the new parity tests; also confirmed proto enum value 0 (REMOTE_NAV_TRIP_ORDER_UNKNOWN) is a legitimately defined value, not a placeholder. No issues found.

Evidence: Cloud REST payload before/after order default (manual REPL check)

cloud call, order omitted -> _request kwargs: {'lat': 37.323, 'lon': -122.0322, 'order': 0}
cloud call, order=2 -> _request kwargs: {'lat': 37.323, 'lon': -122.0322, 'order': 2}

Evidence: New cross-transport parity tests for navigation_gps_request

tests/test_cross_transport_parity.py::NavigationGpsRequestParityTests::test_explicit_order_passes_through_unchanged_on_both_transports PASSED
tests/test_cross_transport_parity.py::NavigationGpsRequestParityTests::test_omitted_order_defaults_to_zero_on_both_transports PASSED

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

✅ **Rebase** - passed

✅ No issues found.

✅ **Review** - passed

✅ No issues found.

✅ **Test** - passed

✅ No issues found.

• uv run pytest tests/test_cross_transport_parity.py -v (6 passed, including the 2 new NavigationGpsRequestParityTests)
• uv run pytest tests (364 passed, full suite)
• Manual REPL check: called VehicleFleet.navigation_gps_request with order omitted and confirmed the outgoing _request json kwargs now contain order: 0 instead of omitting the key; called again with order=2 and confirmed pass-through
• grep proto/car_server.proto to confirm REMOTE_NAV_TRIP_ORDER_UNKNOWN = 0 is a defined enum value on both NavigationGpsRequest and its sibling message

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.