1. Narrow loadConfigForInstall() to catch only INVALID_CONFIG errors,
letting real failures (fs permission, OOM) propagate.
2. Assert allow array is properly cleaned in stale-cleanup test.
3. Add comment clarifying version-resolution is already addressed via
the shared VERSION constant.
4. Run cleanStaleMatrixPluginConfig() during install so
persistPluginInstall() → writeConfigFile() does not fail validation
on stale Matrix load paths.