feat: on-device Meili map matching on Android (trace_attributes) + persistent actor + HTTP tile client

[matt-jsb]

Summary

Three coherent additions to the Android side of the wrapper, all aimed at
enabling Valhalla as a navigation runtime rather than just a routing endpoint:

1. On-device map matching — Valhalla.traceAttributes(...) exposes
   Valhalla's trace_attributes action, backed by Meili's HMM matcher. Useful
   for off-route detection, lane reasoning, and any consumer that needs the
   matched road-graph edge for a sequence of GPS samples.

2. Persistent JNI actor — resolves the existing
   // TODO: Android currently creates a new actor every time. Optimize to be like iOS later. Each Valhalla instance now owns one native
   ValhallaActor for its lifetime (mmap'd tile extract held open). Required
   for any production matching path; routing also benefits.

3. OkHttp-backed ValhallaHttpClient — Android counterpart to the
   existing iOS ValhallaMobileHttpClient. Lets the wrapper pull tiles over
   HTTP when the tile extract isn't bundled locally; consumers pass in their
   own preconfigured OkHttpClient.

A small build-script portability fix (nproc not available on macOS) and an
optional Cloudsmith publishing target ride along — both opt-in and don't
change upstream behaviour by default.

API additions (Android)

Surface	Purpose
Valhalla : Closeable	Lifecycle now explicit. Old construction-without-tiles silently-succeeds-then-fails-per-call behaviour replaced by fail-fast at construction.
Valhalla.traceAttributes(request: TraceAttributesRequest): String	Typed map-matching call. Returns raw JSON for parser flexibility.
Valhalla.traceAttributesRaw(json: String): String	Escape hatch.
com.valhalla.valhalla.mapmatching.*	TraceAttributesRequest, TracePoint, TraceFilters, TraceOptions, ShapeMatch, FilterAction.
OkHttpValhallaHttpClient	Android HTTP tile client.

iOS is unchanged

All edits to src/wrapper/main.cpp are guarded by #ifdef __ANDROID__. The
#elif __APPLE__ block is byte-identical to main. iOS Swift / Obj-C++ APIs
are not touched.

Behaviour change (worth flagging)

Valhalla(context, badConfig) now throws ValhallaException.Internal at
construction time, carrying the original native error message. Previously,
construction succeeded and every subsequent route() returned an error JSON.
The new contract is fail-fast and matches what most Android consumers expect.
Existing tests were updated to match.

Documentation

• android/valhalla/docs/MapMatching.md — request/response shape, off-route
  detection recipe, lifecycle notes.
• android/valhalla/docs/Publishing.md — Cloudsmith publishing recipe (opt-in).

Test plan

• ./gradlew :valhalla:connectedAndroidTest — all existing tests pass,
  plus new ValhallaTraceAttributesTest (smoke test against bundled
  Andorra fixture) and ValhallaHttpTileTest.
• ./gradlew ktfmtCheck — clean.
• Build for all four ABIs (./build.sh android) — clean.
• iOS build untouched — ./build.sh ios still green.

What's not in this PR

• The streaming MapMatcher::AppendMeasurements binding (Path B in the design
  doc) — only worthwhile if profiling shows batch trace_attributes is too
  expensive for live navigation. Deferred until there's evidence.
• iOS bindings for trace_attributes — followable in a separate PR.