Fixes #5338. ListView.MoveUp/MoveDown cycles when TabStop == NoStop

[Copilot]

ListView.MoveDown/MoveUp now wrap around to the opposite end of the list when TabStop == TabBehavior.NoStop, and return false at boundaries when TabStop is anything else.

Proposed Changes/Todos

• MoveDown (ListView.Movement.cs): added Viewport.Height > 0 guard on the scroll-viewport early-return branch (it was spuriously returning true when no frame was set); added TabStop == NoStop branch that selects item 0 instead of returning false
• MoveUp (ListView.Movement.cs): added matching TabStop == NoStop branch that selects the last item instead of returning false
• Added <remarks> XML doc to both MoveDown and MoveUp documenting the wrap-around behavior when TabStop == NoStop and the false-return behavior otherwise
• Added 4 new tests from the issue spec (ListViewTests.cs)
• Updated 4 existing Assert.True(lv.NewKeyDownEvent(Key.Space.WithShift)) assertions to Assert.False at list bottom — they previously passed only because the scroll-guard bug returned true; both Command.Activate (plain-view design, Default View KeyBindings blocking HotKeyBinding #4759) and Command.Down now correctly return false there, while marking side-effects are unaffected

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

Fixes a ListView movement bug and adds wrap-around behavior gated by TabStop. When TabStop == TabBehavior.NoStop, MoveDown at the bottom wraps to the first item and MoveUp at the top wraps to the last; otherwise the methods now correctly return false at the boundary. Also fixes a latent bug where MoveDown returned true from the "scroll viewport" branch when no frame had been set (Viewport.Height == 0).

Changes:

• Add Viewport.Height > 0 guard to MoveDown's scroll-viewport branch so it no longer spuriously returns true with an unset frame.
• Add TabStop == NoStop wrap-around branches in both MoveDown (→ item 0) and MoveUp (→ last item).
• Add 4 new tests for the wrap/return-false behavior and update 4 existing assertions that previously masked the scroll-guard bug.

Reviewed changes

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

File	Description
Terminal.Gui/Views/ListView/ListView.Movement.cs	Adds viewport-height guard and NoStop wrap-around branches in MoveDown/MoveUp.
Tests/UnitTestsParallelizable/Views/ListViewTests.cs	Adds wrap/boundary tests; corrects 4 prior assertions that depended on the buggy true return.