fix(packaging): download sherpa-onnx module before resolving its path

[alohaninja]

Summary

• bundle-dylibs.sh called go list -m to find the sherpa-onnx dylib directory, but on a fresh clone the module isn't in the cache yet — go list silently returns empty, causing LIBDIR to expand to /lib/aarch64-apple-darwin and the build to fail
• Added go mod download github.com/k2-fsa/sherpa-onnx-go-macos before go list so the module is always in the cache before we try to resolve its directory

Startup Error

make start
  go build -o bin/vox ./cmd/vox
  no dylib dir at /lib/aarch64-apple-darwin
  make: *** [app] Error 1

Notes

This doesn't affect the lazy-load design: the dylibs still ship in Contents/Frameworks at build time (required so dlopen can find them when Parakeet is selected), and the model file is still fetched on first use. The go mod download just makes the existing implicit dependency explicit.

Test plan

• Reproduced failure on uncached module (go list returned empty)
• make app succeeds after fix (module downloaded, dylibs bundled, app signed)
• make ci passes (build + vet + race tests)

🤖 Generated with Claude Code