fix: fall back to wrappers when bun compile fails

[malikrohail]

Summary

Fixes the failure mode behind #407 where bun build --compile can fail on virtiofs/devcontainer mounts but ./setup still reports success.

What changed

• Move build orchestration into scripts/build-artifacts.sh
• Replace the blanket || true build tail with explicit build_or_wrap handling
• When bun build --compile fails, write executable bun run wrappers for:
  • browse/dist/browse
  • browse/dist/find-browse
  • bin/gstack-global-discover
• Keep the normal compiled-binary path unchanged when compile succeeds
• Add static coverage for the new build helper in test/gen-skill-docs.test.ts

Why this fixes the bug

On virtiofs mounts, Bun can fail the final rename step for compiled binaries. The old build command hid that failure behind || true, so setup could continue with stale artifacts.

This change makes the failure explicit and recovers by installing wrapper entrypoints instead of leaving stale binaries in place.

Verification

• bun run build
• bun run gen:skill-docs --dry-run
• bun test test/gen-skill-docs.test.ts -t "build script validation"
• bun test

Refs #407