Merge order: 2 of 4

Depends on dotnet10-update (#403). Independent of #405 — the two are sibling branches off dotnet10-update and neither contains the other, so they may be merged in either order.

What this does

The advanced settings block is persisted as JSON with TypeNameHandling.Auto, which means the $type discriminators in the stored settings decide which CLR types get instantiated on load. Without a binder, anyone able to write to the settings file can name an arbitrary type and have it constructed during deserialization.

This adds an allow-list ISerializationBinder (AudioSettingsSerializationBinder) and applies it to both the save and the load path in CUEConfig. The allow-list is derived at runtime from the encoder and decoder settings types that a default CUEConfigAdvanced actually registers, so it stays correct as codecs are added or removed rather than being a hand-maintained list. Anything outside it is rejected with a JsonSerializationException in both directions.

Scope

3 files, +198 / −21.

• CUETools.Processor/CUEConfig.cs — the binder plus its use in Save and Load
• CUETools/CUETools.TestProcessor/CUEConfigSecurityTest.cs — new tests: LoadRejectsUntrustedJsonTypeNames and SaveAndLoadAllowsRegisteredJsonTypeNames
• CUETools/CUETools.TestProcessor/CUETools.TestProcessor.csproj — registers the new test file

Note on reviewing this stack

All four PRs target master, because a cross-fork pull request can only target a branch that exists in this repository. Until #403 merges, this diff also contains its commit.