Rename and enhance existing tests to align with coverage map:
- TestGPUDetectorAMDVendorAlias -> TestAMDAliasManifestRecord
- TestScanArtifacts_SkipsKnownPathsAndLogs -> TestScanExclusionsRecorded
- Add env var expansion verification to TestHIPAAValidation_InlineCredentials
- Record exclusions in manifest.Artifacts for audit trail