Update to TG 2.5.x (PR 5416 preview)

[tig]

⚠️ DO NOT MERGE with the pre-release pin in place

This PR pins a vendored pre-release build (Terminal.Gui 2.5.0-tig-remove-cm-followup.2, built from tui-cs/Terminal.Gui#5416) so the port can be validated ahead of the v2.5.0 release. Before merging, once a public 2.5.x package is on nuget.org:

1. Update the Terminal.Gui pin to the public 2.5.x version in: src/TerminalGuiDesigner.csproj and Showcase/Showcase.csproj
2. Delete local_packages/ and the tgui-pr-5416 package source in nuget.config (delete the file if that source is all it adds)
3. Revert the .gitignore exception for the vendored packages (if present)
4. Re-run build and tests and confirm Terminal.Gui restores from nuget.org

---

Ports TerminalGuiDesigner to the Terminal.Gui 2.5.0 preview as part of the v2.5.0 ecosystem-validation gate (tui-cs/Terminal.Gui#5630).

TEMP: vendored package

Terminal.Gui PR tui-cs/Terminal.Gui#5416 (legacy ConfigurationManager removal) is not yet merged, so 2.5.x is not on nuget.org. This PR vendors a nupkg built from that PR branch:

• local_packages/Terminal.Gui.2.5.0-tig-remove-cm-followup.2.nupkg (+ .snupkg), with a .gitignore exception so they commit
• nuget.config adds a local package source (tgui-pr-5416 → ./local_packages)
• src/TerminalGuiDesigner.csproj and Showcase/Showcase.csproj pin Terminal.Gui to 2.5.0-tig-remove-cm-followup.2 (TEMP comments inline)

Re-vendored 2026-08-22: the original followup.1 package was built from a stale #5416 commit (93c3b3d4) that carried config-load defects fixed later on the branch; followup.2 is built from the #5416 head (e8aba423).

Follow-up: once Terminal.Gui 2.5.x ships on nuget.org, swap the pin to the public package and delete local_packages/ + the nuget.config source. Pattern precedent: tig/winprint#272.

Code changes / API breaks

• No C# source changes were required for the port itself. The entire solution (src, tests, Showcase) compiles clean against the 2.5.0 preview:
  • No legacy ConfigurationManager / ConfigLocations / [ConfigurationProperty] usage in this repo.
  • No View.Text overrides / new-hiding (the 2.5.0 Text CWP change is a no-op here).
  • No IAcceptTarget references (namespace move to Terminal.Gui.Input is a no-op here).
• Review follow-up (one small fix): an audit of string-based reflection over Terminal.Gui internals found ViewExtensions.GetExplicitScheme reflecting a private field "_Scheme" that is actually named _scheme (since at least TG 2.4.5), so the method threw "Scheme private backing field no longer exists" on every call. This was a pre-existing latent defect on v2 (the method currently has no in-repo callers), not 2.5.0 fallout. Fixed test-first to use the public View.HasScheme / View.GetScheme API, with a new regression test (ViewExtensionsTests.TestGetExplicitScheme_NullUntilExplicitlySet). All other reflected members (_commandImplementations, Key.KeyCode, LinearRangeOption Legend/LegendAbbr/Data) were verified present in the 2.5.0 preview.
• Dependency fallout: Microsoft.Extensions.Configuration{,.Binder,.FileExtensions,.Json} bumped 10.0.0 → 10.0.11 to satisfy the Terminal.Gui 2.5.0 dependency floor (NU1605 package-downgrade errors otherwise).

Build / test

• dotnet build src/TerminalGuiDesigner.sln: succeeded, 0 errors (also verified with a clean package cache: restore pulls Terminal.Gui from ./local_packages with no NU1605/NU1608)
• dotnet test (tests/UnitTests, NUnit): 1045 passed, 0 failed, 27 skipped (the skips are pre-existing Assert.Ignore/Assert.Warn known-bug cases in PosTests, MouseManagerTests, AddViewOperationTests, MenuBarTests, and ViewFactoryTests — tests/ is otherwise unchanged vs v2, so all skips predate this port)

🤖 Generated with Claude Code

https://claude.ai/code/session_01BVbLXNzbus2MTXmiJDBErL

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[chatgpt-codex-connector]

Keep the unpublished dependency out of releases

When a version tag triggers the publish step in .github/workflows/build.yml, the packed global tool will declare this preview as a dependency, but nuget.config and local_packages/ are repository-only and the workflow pushes only TerminalGuiDesigner*.nupkg to nuget.org. Because the comment establishes that this Terminal.Gui version is not available there, installing the published tool from the normal source will fail dependency resolution; either prevent preview builds from being published or make the vendored dependency available to package consumers.

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