Fixes #5308. Add editor-oriented Command enum values (Find, Replace, InsertTab, Unindent, FindNext, FindPrevious)

[Copilot]

Fixes

• Fixes Add editor-oriented Command enum values (Find, Replace, InsertTab, Unindent, FindNext, FindPrevious) #5308

The Command enum lacks values needed by text-editing views. Editor projects must handle find/replace and indentation via direct key comparison instead of the KeyBindings system.

Proposed Changes/Todos

• Add InsertTab and Unindent to the Editing Commands region
• Add new Search Commands region with Find, FindNext, FindPrevious, Replace
• Add tests verifying the new values are defined and distinct

New commands:

Command	Description
Find	Opens or activates a find/search UI
FindNext	Finds the next match
FindPrevious	Finds the previous match
Replace	Opens or activates a find-and-replace UI
InsertTab	Inserts a tab character or spaces at the cursor/selection
Unindent	Removes one level of indentation from the current line/selection

These are enum-only additions — no views bind to them yet. Views like TextView, TableView, or external editors can now bind keys to these commands via KeyBindings.Add instead of raw key checks:

KeyBindings.Add (Key.Tab, Command.InsertTab);
KeyBindings.Add (Key.Tab.WithShift, Command.Unindent);
KeyBindings.Add (Key.F.WithCtrl, Command.Find);
KeyBindings.Add (Key.H.WithCtrl, Command.Replace);
KeyBindings.Add (Key.F3, Command.FindNext);
KeyBindings.Add (Key.F3.WithShift, Command.FindPrevious);

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

Adds six new editor-oriented values to the Command enum (InsertTab, Unindent, Find, FindNext, FindPrevious, Replace) so editor-style views can route these actions through the KeyBindings system rather than raw key checks. A new "Search Commands" region groups the find/replace entries; indentation entries go into the existing Editing region. No view bindings are added in this PR — it is a pure enum surface extension.

Changes:

• Add InsertTab and Unindent to the Editing Commands region in Command.cs.
• Add a new Search Commands region with Find, FindNext, FindPrevious, Replace.
• Add a new test file asserting the new enum values are defined and distinct.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Terminal.Gui/Input/Command.cs	Adds the six new enum members and the Search Commands region.
Tests/UnitTestsParallelizable/Input/CommandEnumTests.cs	New tests verifying the new Command values exist and are distinct.