fix: preserve chat input focus during automated file editing (#4574)

- Add preserveFocus: true to showTextDocument call in DiffViewProvider
- Prevents focus from being stolen from chat input during auto-mode file edits
- Update tests to reflect new expected behavior

Fixes #4574

src/integrations/editor/DiffViewProvider.ts

@@ -504,7 +504,7 @@ export class DiffViewProvider {
 			// Pre-open the file as a text document to ensure it doesn't open in preview mode
 			// This fixes issues with files that have custom editor associations (like markdown preview)
 			vscode.window
-				.showTextDocument(uri, { preview: false, viewColumn: vscode.ViewColumn.Active })
+				.showTextDocument(uri, { preview: false, viewColumn: vscode.ViewColumn.Active, preserveFocus: true })
 				.then(() => {
 					// Execute the diff command after ensuring the file is open as text
 					return vscode.commands.executeCommand(

src/integrations/editor/__tests__/DiffViewProvider.spec.ts

@@ -176,7 +176,7 @@ describe("DiffViewProvider", () => {
 			// Mock showTextDocument to track when it's called
 			vi.mocked(vscode.window.showTextDocument).mockImplementation(async (uri, options) => {
 				callOrder.push("showTextDocument")
-				expect(options).toEqual({ preview: false, viewColumn: vscode.ViewColumn.Active })
+				expect(options).toEqual({ preview: false, viewColumn: vscode.ViewColumn.Active, preserveFocus: true })
 				return mockEditor as any
 			})
 
@@ -211,7 +211,7 @@ describe("DiffViewProvider", () => {
 			// Verify that showTextDocument was called with preview: false
 			expect(vscode.window.showTextDocument).toHaveBeenCalledWith(
 				expect.objectContaining({ fsPath: `${mockCwd}/test.md` }),
-				{ preview: false, viewColumn: vscode.ViewColumn.Active },
+				{ preview: false, viewColumn: vscode.ViewColumn.Active, preserveFocus: true },
 			)
 
 			// Verify that the diff command was executed