fix: bake version into binary at build time

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.

.github/workflows/release.yaml

@@ -125,8 +125,8 @@ jobs:
           # Use Docker BuildKit
           export DOCKER_BUILDKIT=1
 
-          # Build the binary using our Dockerfile
-          docker/release/build.sh ${{ matrix.target }}
+          # Build the binary using our Dockerfile with version
+          docker/release/build.sh ${{ matrix.target }} ${{ github.event.inputs.version }}
 
           # Make sure dist directory exists and binary is there
           ls -la dist/