v0.4.6

Added

• JuceAudioBackend — native bridge adapter for the shared web UI.
  Implements the new AudioBackend interface over window.__JUCE__ per
  the nkido-studio bridge protocol v1: readiness handshake, compile via
  native function + compileResult event, and pull-model visualization
  served from buffered pushed frames (playhead, meters, scopeReady
  → scope.bin). Dormant in a plain browser; selected automatically at
  boot when the bridge is present.
• Native bundle build. bun run build:native produces the
  IS_NATIVE bundle (build-native/) for the studio/plugin WebView,
  with a web/src/lib/native/ seam for host-only panels and a
  build-artifact check asserting native-only code never ships in the
  site bundle (and vice versa).
• Per-bus buffer map in akkado::CompileResult. New
  BusBufferMapping list publishing each bus's summed stereo output
  buffer indices, so hosts can tap individual buses and route them to
  separate hardware output channels (prd-bus-routing follow-up).

Changed

• Web audio store split behind an AudioBackend seam. The
  audioEngine store is now a backend-agnostic shell (reactive UI
  state + asset registries) delegating to a WasmAudioBackend that owns
  the worklet/WASM/compile-worker transport — behavior-preserving on the
  site, and the seam both native products (studio + plugin) drive.
  Conformance checklist: docs/audio-backend-conformance.md.