feat(android): assemble vehicle VIN from DashKit CAN stream (2/4)

[dkneeland]

Part 2 of 4 of a stacked series that supersedes #201 (closed; work redistributed across this stack). Base is the GATT-subscribe-retry fix (layer 1), which this PR previously contained — extracted so the reliability fix ships independently.

What & why

Reads the vehicle VIN directly from DashKit's existing BLE CAN notification stream so Tesla enrollment can stop asking the user to type it. Purely additive — no existing behavior changes at this layer.

• VehicleVinAssembler — pure-Kotlin assembler for the muxed VIN frames (bus 1, CAN id 0x405, mux 0x10/0x11/0x12). Accepts segments in any order, tolerates duplicates, rejects short frames / unknown mux / non-ASCII / illegal VIN chars, emits only when all 17 chars validate, resets on teardown. Raw ASCII bytes are joined directly — no 56-bit DBC Double round-trip.
• CanPacket — raw (bus, address, data) tuple parsing extracted from parseAndEmit() so each frame feeds two consumers (dashboard decoder + assembler); firmware build_ble_packet wire format documented alongside the parser.
• DashKitDataSource feeds the assembler per frame; exposes vinState.
• ConnectionViewModel.vehicleVin — dedicated replaying flow; deliberately not added to CarState (stays out of the dash-app data contract); reset during connection teardown.

Inert until layer 4 consumes the flow.

Tests

Assembler unit tests (ordering, duplicates, special mux-A offsets, malformed input) and parser/data-source integration tests (single/multi-notification assembly, batching, truncated packets). Full testDebugUnitTest green at carve time against main @ b506147.

Stack & merge order

Order	Layer	Base
1	GATT subscribe-retry fix	main
2	this PR	layer 1
3	Tesla BLE core	layer 2
4	VIN-driven enrollment UX	layer 3

Merge bottom-up after layer 1; the managed stack handles retarget/rebase automatically.

[dkneeland]

Reworked per @wpmed92's review (force-pushed as a single commit; layers 3/4 rebased on top):

• VIN assembly is now native.
  epo/bridge/car/vin_assembler.h\ (header-only) is driven from \VehicleDecoder::updateFrame(), so it rides the existing decode path — no special-case Kotlin, no extra pass.
• Raw-byte reads, deliberately: VIN_B405/VIN_C405 are 56-bit, wider than double's 53-bit mantissa; the normal \Signal::getValue()\ route corrupts the top byte(s), so the assembler reads raw frame bytes and validates ASCII there.
• Next to CarState, not inside it: CarState is a fixed \DoubleArray\ across JNI that flows to dash apps; the plan keeps the VIN out of dash-app data/persistence/logs. It's surfaced via a dedicated
  ativeGetVin() -> String?\ /
  ativeResetVin()\ JNI pair instead of packing ASCII into the numeric array.
• No downstream churn: \DashKitDataSource.vinState\ + teardown resets unchanged; \VehicleVinState\ stays in Kotlin as the flow type; feat(android): Tesla BLE core - client, status source, VIN-matched scanner (3/4) #212/feat(android): VIN-driven Tesla enrollment UX (4/4) #213 rebased with zero code changes.
• Coverage moved native too: Kotlin assembler tests deleted; ported into \�ridge/tests/vin_assembler_test.cpp, a host-run CMake/CTest target for non-Android builds (\cmake -B build-host && cmake --build build-host && ctest). Android build path unchanged via an \if(ANDROID)\ guard in bridge/CMakeLists.txt.

Validation: host assembler unit tests pass; decoder-integration check exercised updateFrame→assembler through the real VehicleDecoder; full :app:testDebugUnitTest\ green at every layer of the rebuilt stack.

[wpmed92]

@dkneeland I updated with how I suggested, but I think maybe I didn't communicate it clearly.
What I wanted is to have the vin done in car state mapper. Now our dbc parser can return raw u64, and the everything happens in the car_state layer, with vin bytes packed into doubles, then assembly in Kotlin (well, it's not much assembling really, more like just unpacking from the doubles):
This removes all of these: VinAssembler, nativeGetVin/nativeResetVin, VehicleVinState, t hevinState/vehicleVin StateFlows and all reset plumbing.