## Why
An installer can retarget the selected executable symlink or junction while an app server is running. Recording the launch-time identity preserves which binary was started after that path changes.
## What changed
- Resolve the executable path before launching on all platforms and store an optional executable identity in app-server PID records. Continue accepting older records without this field and expose the identity only for an active process.
- Use BLAKE3 for executable identity digests and make `ExecutableIdentity` serializable.
- Schedule updater checks with an explicit deadline in `tokio::select!`, preserving persisted update intervals, settings-error retries, and termination handling.
## Testing
Add a Unix test that verifies the recorded identity matches the resolved launch binary, differs from a retargeted symlink's binary, and remains optional when reading legacy PID records.
GitOrigin-RevId: 4821130b9a5e75b417a8e39c583b30427a872ff8
Eric Traut
769a6a5bcd