## What changed
- Add an embedded `defaults.toml` and always install it as the lowest-precedence configuration layer when no packaged-defaults path is supplied.
- Keep packaged defaults out of config RPC layer and origin metadata.
- Report a user setting as overridden only when the effective layer has higher precedence, so clearing a setting can fall back to its packaged default without a false override.
## Testing
- Cover loading the packaged layer when other configuration files are absent.
- Cover config RPC filtering and clearing a user value that falls back to a packaged default.
GitOrigin-RevId: c1c0e1e681e4ac1be2602550972533443c5df51b
