## What changed
- Resolve manifest-declared metric operations against the executor filesystem for remote plugin commands.
- Create the measurement sidecar in an executor-native, owner-private temporary directory, stream its bounded output back for validation, and clean up the directory afterward.
- Extend the exec-server protocol with the executor temporary directory and atomic private-directory creation.
## Testing
- Cover remote unified-exec measurements for foreground and background commands.
- Verify private directories use owner-only permissions on Unix and fail closed on unsupported platforms.
GitOrigin-RevId: dbbd0a84717b91237fc5728e510e18994eb46dd4
9579479d28