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.