Fixes #macOS-tests-failing. Deep-clone hard-coded config cache values at initialization to prevent mutation corruption

[Copilot]

ConfigurationManager._hardCodedConfigPropertyCache stored a shared reference to Application.DefaultKeyBindings (a Dictionary<Command, PlatformKeyBinding>). In-place mutations like Application.DefaultKeyBindings![Command.Quit] = Bind.All(Key.X.WithCtrl) silently corrupted the "hard-coded default" cache, since both pointed to the same object. On macOS, test ordering caused Load_And_Apply_HardCoded to run before any Disable(true) → Apply() call that would have created a new dictionary and broken the shared reference — producing Actual: Ctrl+X where Expected: Esc.

Proposed Changes/Todos

• In ConfigurationManager.Initialize(), deep-clone each PropertyValue immediately after UpdateToCurrentValue(), before marking the cache entry Immutable = true:

hardCodedProperty.Value.Immutable = false;
hardCodedProperty.Value.UpdateToCurrentValue ();
hardCodedProperty.Value.PropertyValue = DeepCloner.DeepClone (hardCodedProperty.Value.PropertyValue);
hardCodedProperty.Value.Immutable = true;

This ensures the cache stores independent copies of reference-type values so in-place mutations to static properties (e.g. Application.DefaultKeyBindings![cmd] = ...) cannot corrupt the hard-coded defaults regardless of test execution order.

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working

Original prompt

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This section details on the original issue you should resolve

<issue_title>macOS tests failing</issue_title>
<issue_description>This is likely due to some test incorrectly setting global keybindings state.

2026-03-23T14:14:33.4081250Z ##[group]Run dotnet test
2026-03-23T14:14:33.4081590Z �[36;1mdotnet test \�[0m
2026-03-23T14:14:33.4081850Z �[36;1m --project Tests/UnitTests.NonParallelizable \�[0m
2026-03-23T14:14:33.4082160Z �[36;1m --no-build \�[0m
2026-03-23T14:14:33.4082320Z �[36;1m --verbosity normal \�[0m
2026-03-23T14:14:33.4082640Z �[36;1m --diagnostic --diagnostic-output-directory logs/UnitTests.NonParallelizable/macOS�[0m
2026-03-23T14:14:33.4116490Z shell: /bin/bash --noprofile --norc -e -o pipefail {0}
2026-03-23T14:14:33.4116710Z env:
2026-03-23T14:14:33.4116910Z DisableRealDriverIO: 1
2026-03-23T14:14:33.4117130Z DOTNET_ROOT: /Users/runner/.dotnet
2026-03-23T14:14:33.4117300Z ##[endgroup]
2026-03-23T14:14:33.9793930Z Running tests from /Users/runner/work/Terminal.Gui/Terminal.Gui/Tests/UnitTests.NonParallelizable/bin/Debug/net10.0/UnitTests.NonParallelizable.dll (net10.0|arm64)
2026-03-23T14:14:34.5257770Z �[31mfailed�[m UnitTests.NonParallelizable.ConfigurationTests.ConfigurationMangerTests.Load_And_Apply_HardCoded �[90m(30ms)�[m
2026-03-23T14:14:34.5258920Z Assert.Equal() Failure: Values differ
2026-03-23T14:14:34.5261050Z Expected: Esc
2026-03-23T14:14:34.5261530Z Actual: Ctrl+X
2026-03-23T14:14:34.5262400Z from /Users/runner/work/Terminal.Gui/Terminal.Gui/Tests/UnitTests.NonParallelizable/bin/Debug/net10.0/UnitTests.NonParallelizable.dll (net10.0|arm64)
2026-03-23T14:14:34.5263250Z �[31m Assert.Equal() Failure: Values differ
2026-03-23T14:14:34.5263530Z Expected: Esc
2026-03-23T14:14:34.5263730Z Actual: Ctrl+X
2026-03-23T14:14:34.5264890Z �[m�[90m at UnitTests.NonParallelizable.ConfigurationTests.ConfigurationMangerTests.Load_And_Apply_HardCoded() in /Users/runner/work/Terminal.Gui/Terminal.Gui/Tests/UnitTests.NonParallelizable/Configuration/ConfigurationMangerTests.cs:951�[90m
2026-03-23T14:14:34.5265950Z at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
2026-03-23T14:14:34.5266580Z at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
2026-03-23T14:14:34.5407920Z �[m�[31mfailed�[m UnitTests.NonParallelizable.ConfigurationTests.ConfigurationMangerTests.ResetToHardCodedDefaults_and_Load_LibraryResourcesOnly_are_same �[90m(17ms)�[m
2026-03-23T14:14:34.5408690Z Assert.Equal() Failure: Values differ
2026-03-23T14:14:34.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes macOS tests failing #4846

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