## Why
Repository manifests and user-configured sources must not be able to claim names reserved for managed or remote marketplaces.
## What changed
- Reject reserved marketplace names from unmanaged sources during discovery, installation, configuration projection, and configured marketplace upgrades, even when source restrictions are disabled.
- Recognize managed marketplaces only at their expected paths. Preserve the required macOS and Windows path equivalences without allowing symlink aliases to inherit managed provenance.
## Testing
- Cover reserved-name rejection for plugin list and install RPCs, configured upgrades, unrestricted policy, and remote marketplace names.
- Cover symlink spoofing and Windows managed-path normalization.
GitOrigin-RevId: a610bdc382857f306dd3e244f0992de2ec279673
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