feat: add openTabsAtEndOfList setting to control tab placement

[roomote]

This PR implements the feature requested in issue 6006 to add a user setting that controls where new Roo tabs open in VS Code.

Changes:

• Added openTabsAtEndOfList setting to the global settings schema with default value false
• Updated ClineProvider to include the setting in state management and pass it to webview
• Modified DiffViewProvider to use ViewColumn.Beside when the setting is enabled, which opens tabs at the end of the tab list
• Added test coverage for the new setting

When openTabsAtEndOfList is set to true, the extension will use vscode.ViewColumn.Beside instead of vscode.ViewColumn.Active when opening diff views and showing documents. This causes VS Code to open new tabs at the end of the current tab group rather than next to the active tab.

This is particularly useful for users who have disabled the workbench.editor.focusRecentEditorAfterClose setting and want to maintain their tab order without new tabs disrupting their workflow.

Fixes #6006

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Important

Adds openTabsAtEndOfList setting to control tab placement in VS Code, affecting DiffViewProvider and Task behavior.

• Behavior:
  • Adds openTabsAtEndOfList setting to global settings schema with default false.
  • Modifies DiffViewProvider to use vscode.ViewColumn.Beside when setting is true, opening tabs at the end of the tab list.
  • Updates Task to initialize DiffViewProvider with openTabsAtEndOfList setting.
• State Management:
  • ClineProvider includes openTabsAtEndOfList in state management and passes it to webview.
• Testing:
  • Adds test for openTabsAtEndOfList in index.test.ts.
• Misc:
  • Updates Task.spec.ts to mock onDidChangeWorkspaceFolders and Uri methods.

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[daniel-lxs]

To be implemented by @felixAnhalt, closing