Restore #5243 AOT fix lost in #5246 merge resolution

[tig]

Summary

The fix from #5243 ("Fixes #5259. AOT: use source-generated JSON serializer for dictionary construction in DeepCloner") was reverted when commit 94dca985d merged origin/main back into release/v2.1.0-rc.1. That merge had conflicts in DeepCloner.cs and ConfigurationManager.cs and the resolution picked main's pre-#5243 versions, silently dropping the fix.

PR #5246 (rc.1 → main) and PR #5247 (rc.1 backmerge → develop) then carried the broken state forward. v2.1.0-beta.1 was tagged before #5243 merged (no fix); v2.1.0-rc.1 was tagged after, but doesn't have it either because of the conflict resolution.

This PR restores Terminal.Gui/Configuration/DeepCloner.cs and Terminal.Gui/Configuration/ConfigurationManager.cs to their state at 11d6e27d7 (the original #5243 merge commit). The two files were checked out from that commit; no other changes.

Diff content

DeepCloner.cs — adds back the 26-line SourceGenerationContext.GetTypeInfo → JsonSerializer.Deserialize(\"{}\", typeInfo) fallback in CreateDictionaryInstance (between the typed paths and Activator.CreateInstance), plus the // Typed paths… comment.

ConfigurationManager.cs — removes the 54-line per-type clone helpers (CloneHardCodedPropertyValue, CloneKeyBindings, ClonePlatformKeyBinding, CloneKeyArray) and reverts the call site back to DeepCloner.DeepClone(...). Generic dictionary handling lives in DeepCloner again.

Net: +28 / -53.

Repro before the fix (current develop)

dotnet publish Examples/NativeAot -c Release -r win-x64 --self-contained
./bin/Release/net10.0/win-x64/publish/NativeAot.exe

Crashes at module init:

Unhandled exception. System.MissingMethodException: No parameterless constructor defined for type
'System.Collections.Generic.Dictionary`2[Terminal.Gui.Drawing.ColorName16,System.String]'.
   at DeepCloner.CreateDictionaryInstance(...)
   at ConfigurationManager.Initialize() ...
   at RunModuleInitializers()

Same crash a downstream AOT consumer (gui-cs/clet) hit. Tracked through #5239 → #5240 (partial fix) → #5242 (residual) → #5243 (the right fix) → #5248 (filed when rc.1 still crashed — explained by this PR).

Verification

Build and pack of TG with this branch checked out:

dotnet build Terminal.Gui/Terminal.Gui.csproj -c Release    # 0 errors
dotnet pack  Terminal.Gui/Terminal.Gui.csproj -c Release --no-build --output local_packages

Then in gui-cs/clet on feature/makefile-releases, pinning <PackageReference Include=\"Terminal.Gui\" Version=\"2.1.1-aot-debug-5248.1\" />:

dotnet publish src/Clet -c Release -r win-x64 --self-contained -p:PublishAot=true -o publish/win-x64
./publish/win-x64/clet.exe --version    # was crashing against rc.1; now: 1.0.0-alpha (Terminal.Gui 2.1.1-aot-debug-5248.1), exit 0
./publish/win-x64/clet.exe list         # all 17 clets enumerate, exit 0

How to make sure this stays fixed

PR #5243 added a Dictionary<ColorName16, string> test in DeepClonerTests.cs — that test was retained through the merges (verified). However, the test runs in a non-AOT context and so does not exercise the actual AOT trim path that broke. An AOT regression test (publish Examples/NativeAot in CI and run it) would have caught this conflict-resolution regression. PR #5243's commit log mentions adding such CI; if it didn't make it through the same merge, that's a separate follow-up.

Linked

• Fixes (re-fixes): docs: add clet to showcase #5259
• Refs AOT: ConfigurationManager.Initialize crashes with MissingMethodException on Dictionary<Command, PlatformKeyBinding> #5239, AOT: ConfigurationManager.Initialize still crashes on Dictionary<ColorName16, string> after #5240 #5242, Fixes #5259. AOT: use source-generated JSON serializer for dictionary construction in DeepCloner #5243, AOT: #5243 fix not effective at runtime — Dictionary<ColorName16, string> still crashes in 2.1.0-rc.1 #5248
• Conflict-merge cause: 94dca98
• Affected tags: v2.1.0-beta.1 (separate cause), v2.1.0-rc.1 (this conflict)

cc @tig

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