feature: add option to show launcher tabs vertically

[ara-hwang]

Title: feature: add option to show launcher tabs vertically

Base: sourcegit-scm/sourcegit:develop ← Head: ara-hwang/sourcegit:feature/vertical-tabs-upstream

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Description

This PR adds a new appearance option: Preferences › Appearance › Show tabs vertically.

When it is enabled, the page tabs are removed from the titlebar and shown as a vertical list on the left side of the main window. This is similar to the vertical tabs layout found in browsers and editors.

The option is disabled by default, so nothing changes for existing users.

Motivation

• When many repositories are open, the horizontal tabs either shrink or overflow and need scrolling (see the first screenshot). A vertical list shows many more tabs at once.
• Long repository names are easier to read, because a vertical tab can be much wider than a horizontal one.
• Wide screens usually have spare horizontal space, while vertical space is limited.

Screenshots

Default (unchanged): horizontal tabs overflow with 7 repositories open

Vertical tabs

Vertical tabs (dark theme)

New option in Preferences › Appearance	Context menu in vertical mode

Changes

• ViewModels/Preferences.cs: adds the persisted property UseVerticalTabs (default false).

• ViewModels/LayoutInfo.cs: adds LauncherVerticalTabsWidth (default 200), which stores the width of the vertical tab bar.

• Views/Preferences.axaml: adds a checkbox to the Appearance tab, below Use fixed tab width in titlebar.

• Views/LauncherVerticalTabBar.axaml(.cs) (new): the vertical tab bar.

  • Each tab shows the same information as a horizontal tab: bookmark color, repository name, dirty-state dot and close button. Long names are trimmed, and the tooltip shows the full path.
  • A Create New Tab button sits at the bottom. It reuses the existing Text.PageTabBar.New string.

• Views/LauncherTabBarBase.cs (new): the shared tab behaviors moved here from LauncherTabBar without logic changes, so both tab bars use the same code. These behaviors are:

  • middle-click to close
  • drag to reorder
  • the tab context menu
  • the close button

  The only difference is the context menu item that closes the following tabs. In vertical mode it reads Close Tabs Below instead of Close Tabs to the Right.

• Views/Launcher.axaml(.cs): when the option is enabled, hides the titlebar tabs and shows the vertical tab bar in a left column. The workspace and page-switcher buttons stay in the titlebar.

  • The column is resized with a GridSplitter (min 120 / max 480) and the width is persisted.
  • This works the same way as the repository sidebar: IsVerticalTabsVisible / VerticalTabsWidth mirror IsNormalSidebarVisible / SidebarWidth in Repository.axaml.cs.

• Resources/Locales: adds Text.Preferences.Appearance.UseVerticalTabs and Text.PageTabBar.Tab.CloseBelow to all 16 locales. Only en_US and ko_KR were written by native speakers, so translators are welcome to improve the others.

Test

• dotnet build -c Release: 0 errors and 0 warnings.
• dotnet format --verify-no-changes src/SourceGit.csproj passes.
• Checked on Linux (Xvfb) with several repositories open:
  • Clicking a vertical tab switches the active page.
  • Drag to reorder works in both vertical and horizontal mode, which checks that the refactor did not break it.
  • Dragging the splitter resizes the bar, and the width is restored after a restart.
  • The context menu shows Close Tabs Below in vertical mode.
  • Turning the option off brings back the existing titlebar tabs unchanged.
• Windows: tested on Windows 11 x64
• macOS: not tested.