Fixes #5125 - Preserve FileDialog selection colors when navigating via dotdot

[Copilot]

Navigating up from a subdirectory via the .. row could change the selected row background in FileDialog. This updates FileDialog-specific table coloring so file-type colors do not override the table’s selected-state scheme.

Proposed Changes/Todos

• Keep selection-state colors owned by TableView

  • FileDialog.ColorGetter now preserves the row scheme’s Focus/Active/Disabled attributes instead of rebuilding selected-state colors from file-type colors.
  • This keeps the .. row visually consistent before and after navigating up.

• Add a focused regression test

  • Added a unit test covering the parent-row (..) path from a subdirectory and asserting the effective selected-state scheme is preserved.

return new Scheme
{
    Normal = new Attribute (foreground, background),
    HotNormal = new Attribute (foreground, background),
    Focus = args.RowScheme.Focus,
    HotFocus = args.RowScheme.HotFocus,
    Active = args.RowScheme.Active,
    HotActive = args.RowScheme.HotActive,
    Disabled = args.RowScheme.Disabled
};

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

[Copilot]

Pull request overview

This PR fixes a visual inconsistency in FileDialog where navigating up via the .. row could cause selected-row background colors to change unexpectedly. It does so by ensuring FileDialog’s per-cell coloring does not override TableView’s selection-state scheme.

Changes:

• Update FileDialog’s table ColorGetter to preserve TableView’s selection-state attributes (Focus/HotFocus/Active/HotActive/Disabled) instead of recomputing them from file-type colors.
• Add a regression unit test that exercises the .. (parent) row coloring behavior from a subdirectory state.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
Terminal.Gui/Views/FileDialogs/FileDialog.TableView.cs	Preserve TableView-owned selection/active/disabled scheme roles when applying file-type coloring.
Tests/UnitTestsParallelizable/Views/FileDialogColorTests.cs	Add regression coverage ensuring the parent-row color getter retains selection/active scheme roles.

[BDisp]

Nice.