Enhancement: Ctrl+Tab / Ctrl+Shift+Tab cycles through tabs in the current workspace

[JoshuaRowePhantom]

Summary

Ctrl+Tab should activate the next tab in the current workspace pane; Ctrl+Shift+Tab should activate the previous tab. This mirrors the convention in browsers, VS Code, and other tabbed applications.

Proposed implementation

Follows the same pattern as #50 (Ctrl+W):

1. Add ActivateNextTabCommand and ActivatePreviousTabCommand to MainWindowViewModel, each as a no-parameter RelayCommand:

   • Find the active workspace pane's document dock.
   • Collect documentDock.VisibleDockables.OfType<WorkspaceDocument>() as an ordered list.
   • Find the index of documentDock.ActiveDockable.
   • Advance (or retreat) by one, wrapping around at both ends.
   • Call dockFactory.SetActiveDockable(nextDocument) and dockFactory.SetFocusedDockable(documentDock, nextDocument).

2. Register KeyBindings in MainWindow.axaml:

   <Window.KeyBindings>
       <KeyBinding Gesture="Ctrl+Tab"       Command="{Binding ActivateNextTabCommand}" />
       <KeyBinding Gesture="Ctrl+Shift+Tab" Command="{Binding ActivatePreviousTabCommand}" />
   </Window.KeyBindings>

Notes

• Both commands are no-ops when the workspace has fewer than two tabs.
• Avalonia window-level KeyBindings fire after the focused control has had a chance to handle the key, so controls that mark Ctrl+Tab as handled will suppress the binding naturally.
• Cycle order should follow the visual tab strip order (VisibleDockables index), not MRU order, to be predictable.

Affected files

• Phantom.Workspaces/ViewModels/MainWindowViewModel.cs — add ActivateNextTabCommand, ActivatePreviousTabCommand
• Phantom.Workspaces/MainWindow.axaml — add KeyBinding entries for Ctrl+Tab and Ctrl+Shift+Tab

[JoshuaRowePhantom]

Fixed: Ctrl+Tab / Ctrl+Shift+Tab cycle tabs via CycleTabForwardCommand / CycleTabBackwardCommand with wrap-around. KeyBindings added to MainWindow.axaml.

[JoshuaRowePhantom]

Verification passed

Checked: Commit 93de41d (Fix #50 + #51), files Phantom.Workspaces/ViewModels/MainWindowViewModel.cs, Phantom.Workspaces/MainWindow.axaml, and Phantom.Workspaces.Tests/MainWindowIntegrationTests.cs on the eatures branch.

Result: Implementation found, all verification criteria satisfied, tests present and green.

• CycleTabForwardCommand and CycleTabBackwardCommand added to MainWindowViewModel as RelayCommand properties, both delegating to OnCycleTab(int delta).
• OnCycleTab collects documentDock.VisibleDockables, finds the current index, and advances/retreats with modular wrap-around; no-ops when fewer than 2 tabs.
• KeyBinding entries for Ctrl+Tab → CycleTabForwardCommand and Ctrl+Shift+Tab → CycleTabBackwardCommand added to MainWindow.axaml.
• Tests cover: forward cycle with wrap-around (CycleTabForwardCommand_WithThreeTabs_WrapsAroundForward), backward cycle with wrap-around (CycleTabBackwardCommand_WithThreeTabs_WrapsAroundBackward), and single-tab no-op (CycleTabForwardCommand_WithSingleTab_IsNoOp).
• No disabled/quarantined tests, no unresolved TODOs, no timing-dependent synchronization.