Reject unsafe archive entry keys at indexing

[esnya]

Summary

• normalize archive entry keys at the archive indexing boundary instead of converting missing keys to empty paths
• skip empty, absolute, drive-rooted, and traversal archive entries before they can surface through dataset file lookup
• cover unsafe archive entries so only safe dataset-relative paths are indexed

Verification

• dotnet restore PlateauResoniteLink.sln --locked-mode --disable-build-servers
• dotnet format whitespace . --folder --verify-no-changes
• dotnet build PlateauResoniteLink.sln --configuration Release --no-restore --disable-build-servers -m:1 -p:UseSharedCompilation=false
• dotnet test PlateauResoniteLink.sln --configuration Release --no-restore --verbosity normal -m:1 --disable-build-servers -p:UseSharedCompilation=false (1007 passed)
• Fake Live Sink canonical dump for plateau-13213-higashimurayama-shi-2020, mesh 53395325, packages dem,bldg, terrain mesh grid matched the baseline with git diff --no-index; temp dump removed