build(moonshine): compile moonshine C++ core from source, eliminating libmoonshine dependency

[staging-devin-ai-integration]

build(moonshine): compile C++ core from source via cc crate

Summary

Fixes the rust-lld: error: unable to find library -lmoonshine build failure by replacing the dynamic linking approach with building the moonshine C++ core from source during cargo build.

Before: build.rs emitted cargo:rustc-link-lib=moonshine, requiring users to manually build and install libmoonshine.so from the moonshine repo via CMake. The moonshine project doesn't publish pre-built Linux x86_64 shared libraries, so this always failed out of the box.

After: build.rs downloads moonshine v0.0.49 source from GitHub, compiles all 17 C++ source files into a static archive (libmoonshine_core.a) using the cc crate, and links statically. ONNX Runtime remains a dynamic dependency (libonnxruntime.so) — discovered from system paths or auto-downloaded from Microsoft's GitHub releases.

Key changes:

• build.rs: Full rewrite (~300 lines). Downloads/caches moonshine source, finds/downloads ORT with version validation, compiles C++ with cc, sets RPATH=$ORIGIN. Uses cargo:warning= messages so download/compile progress is visible during builds (first build downloads ~100MB and compiles 17 C++ files, which takes a few minutes).
• Cargo.toml: Added cc = "1.2" build-dependency
• plugins.yml: Added lint-moonshine CI job and moonshine format check
• verify_bundles.py: Added moonshine bundle portability check for libonnxruntime.so
• ConvertView.tsx: Added moonshine to transcription pipeline detection
• moonshine-stt.yml: Fixed model reference to match plugin.yml

Environment variable overrides: MOONSHINE_SRC_DIR (local source checkout), ORT_LIB_DIR (pre-installed ORT location).

Updates since last revision

• ORT version validation: find_or_download_onnxruntime() now checks the version of any system libonnxruntime.so by parsing versioned symlinks (e.g., libonnxruntime.so.1.17.1). Incompatible versions are skipped with a warning, and the correct ORT 1.23.2 is downloaded automatically. Previously, any system ORT was accepted regardless of version, causing a runtime segfault when moonshine (requiring ORT API v23) loaded an older ORT (e.g., 1.17.1). If ORT_LIB_DIR is set explicitly with an incompatible version, the build panics with a clear error message.
• Convert UI fix: Added plugin::native::moonshine to checkIfTranscriptionPipeline() in ConvertView.tsx so the Convert UI shows the transcription display instead of the audio playback/download interface when running the moonshine sample pipeline.
• Sample pipeline fix: Updated moonshine-stt.yml to reference moonshine-base-en / model_arch: base instead of moonshine-tiny-en / model_arch: tiny. The previous reference didn't match any model defined in plugin.yml, which was contributing to the "Plugin failed to create instance" runtime error.
• Switched all progress messages from eprintln! to println!("cargo:warning=...") so users see download and compilation progress during cargo build instead of a frozen progress bar.

Review & Testing Checklist for Human

• End-to-end runtime test: Build the plugin (just build-plugin-native-moonshine), load the moonshine sample pipeline in Convert, upload an audio file, and verify transcription output appears. Critical: While the ORT version mismatch and model path issues are now fixed, the pipeline hasn't been tested with actual audio. There may be additional runtime issues (model file structure, initialization, etc.).
• ORT version detection edge case: On systems where libonnxruntime.so exists without versioned symlinks (e.g., custom installs), ort_version_from_dir() returns None and the system ORT is skipped. Verify this behavior is acceptable, or if we should add readelf -d fallback to check SONAME.
• Verify the 17 hardcoded .cpp filenames match moonshine v0.0.49's actual source tree. The list was derived from their CMakeLists.txt but any mismatch will cause build failures. Cross-reference with https://github.com/moonshine-ai/moonshine/tree/v0.0.49/core
• Verify Convert UI: Load the moonshine sample pipeline and confirm the UI shows "Transcribe Audio" button and transcription output display (not audio playback controls). This was tested visually but not with actual transcription output.
• Build requirements: Build requires curl and tar on the host. These are standard on Linux but the build script will panic if they're missing. Verify this is acceptable.

Notes

• Build was verified locally: cargo build --release succeeds, cargo clippy -- -D warnings passes, cargo fmt passes, all 212 project tests pass
• UI fix was tested visually: the Convert page correctly detects the moonshine pipeline as a transcription pipeline and shows the "Transcribe Audio" button instead of audio playback/download controls (see screenshot: )
• ORT version checking was tested locally: On a system with ORT 1.17.1, cargo build now correctly skips the old version with warning "Skipping onnxruntime 1.17 at /usr/local/lib (need 1.23)" and downloads ORT 1.23.2 instead. The segfault is resolved.
• Runtime testing of the actual transcription pipeline was NOT performed — only the build system, UI detection logic, and ORT version checking were validated. The sample pipeline needs end-to-end testing with actual audio to verify model loading and transcription work correctly.
• The approach mirrors how whisper-rs builds whisper.cpp from source
• Linux x86_64 only: The ORT download fallback hardcodes onnxruntime-linux-x64. Confirm this is acceptable or if macOS/ARM support is needed.

Requested by @streamer45 · Devin session

[staging-devin-ai-integration]

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