Instead of hacking around the version in the Node.js wrapper script,
properly pass the version at build time via SANDBOX_AGENT_VERSION env var.
Changes:
- build.rs: Generate version.rs with VERSION constant from env var
- main.rs: Use generated version constant for clap --version
- Dockerfiles: Accept SANDBOX_AGENT_VERSION as build arg
- build.sh: Pass version as second argument to Docker builds
- release.yaml: Pass version to build script during CI
- Remove version hack from sdks/cli/bin/sandbox-agent wrapper
The version is now baked into the binary during the release build,
ensuring --version reports the correct npm package version.
## Summary
- Add Node.js build stage to all release Dockerfiles to build the inspector frontend
- Copy pre-built inspector assets into Rust build stages so they get embedded in binaries
- Remove `SANDBOX_AGENT_SKIP_INSPECTOR=1` from all Dockerfiles and the release workflow
## Test plan
- [ ] Build linux-x86_64 locally: `docker/release/build.sh x86_64-unknown-linux-musl`
- [ ] Run the binary and verify inspector is embedded (should show "inspector ui available")
- [ ] Access the inspector UI at http://localhost:2468/ui/🤖 Generated with [Claude Code](https://claude.ai/code)
