Add ANSI statusline support

[Copilot]

Fixes

Terminal.Gui can now render lightweight status information to ANSI terminal chrome/title regions, and can run a one-row app entirely through that statusline render path.

Proposed Changes/Todos

• Application API

  • Added IApplication.StatusLine / Application.StatusLine.
  • Added graceful no-op behavior when the active driver cannot emit ANSI statusline output.

• Statusline-only mode

  • Added AppModel.StatusLine.
  • Constrains the app surface to one terminal-width row and emits rendered content via OSC title/statusline output.

• UICatalog coverage

  • Added ANSI StatusLine for secondary statusline output from a normal app.
  • Added ANSI StatusLine Only for whole-app statusline rendering.

using IApplication app = Application.Create ();
app.Init ();

app.StatusLine.SetText ("Build: passing", mode: 2);

using IApplication app = Application.Create ();
app.AppModel = AppModel.StatusLine;
app.Init ();

app.Run<MyStatusLineRunnable> ();

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

[tig]

@BDisp would you please try this out locally?

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Fall back to normal refresh when statusline output unsupported

When AppModel.StatusLine is active, Refresh() always returns immediately after SetTerminalTitle(...); on legacy consoles (IsLegacyConsole == true), SetTerminalTitle is a no-op, so the method exits without drawing anything at all. This makes statusline-mode apps completely invisible on unsupported terminals (for example Windows consoles without VT), rather than degrading gracefully. Consider checking support before early-returning and using the normal buffer render path when title/statusline output is unavailable.

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[tig]

@copilot if someone tries to use appmodel.statusline on a legacy term, an exception should be thrown.