Migrate protobuf layer to @teslemetry/tesla-protocol (ts-proto API)

[Bre77]

What

• Replace the bundled src/pb2/* protobuf types + google-protobuf runtime with the published @teslemetry/tesla-protocol package.
  • @teslemetry/tesla-protocol is ts-proto generated: plain-object messages with Type.create() / Type.encode().finish() / Type.decode(), not google-protobuf's .setX()/.serializeBinary() classes.
  • The only real protobuf call site in the library is Session in src/vehiclesigned.ts (builds/tags the HMAC-personalized signature for signed commands); it's ported to the new API and HMAC_Personalized_Signature_Data is now HMACPersonalizedSignatureData from @teslemetry/tesla-protocol/command/signatures.
  • src/pb2/* and the google-protobuf/ts-protoc-gen dependencies are removed.
• Fix three pre-existing bugs that left the repo unable to build or typecheck at all (found while reproducing a green build for this migration, all from the same "loadPrivateKey" commit):
  • src/vehiclesigned.ts had a stray closing brace that ended the VehicleSigned class early, leaving every command method declared outside any class.
  • src/teslafleetapi.ts had an unbalanced brace in loadPrivateKey, leaving TeslaFleetApi's class body unclosed.
  • src/vehiclesigned.ts and src/vehiclespecific.ts imported FleetTelemetryConfig from a ./types/fleet_telemetry_config.js module that doesn't exist (the type actually lives in ./types/commands.js); once the import path was fixed, a second latent bug surfaced where the wrapper type ({ vins, config }) was used in place of just its config field.
• Add moduleResolution: NodeNext alongside module: NodeNext in tsconfig.json. Without it, TypeScript's classic resolution can't see the exports map that scoped packages like @teslemetry/tesla-protocol (and even @types/node's own internals) gate their subpath types behind, so nothing in node_modules resolved.
• Bump typescript/@types/node to versions whose Uint8Array typings are generic, matching what @teslemetry/tesla-protocol's own @bufbuild/protobuf runtime dependency expects.

No public API or behavior change - this is an internal proto-source swap. pnpm install (which runs tsc via prepare) and npx tsc --noEmit are both clean; there's no test suite in this repo yet.