Fix "open changes in diff editor"

[alexr00]

Fixes #314685

[Copilot]

Pull request overview

This PR fixes Chat’s “Open Changes in Diff Editor” action so it works even when the currently active editor is a webview (e.g. GHPR description), by ensuring the action opens the target file’s editor pane before toggling the diff UI.

Changes:

• Stop using editorService.activeEditorPane as the target pane for diff toggling.
• Always openEditor({ resource: uri }) for the file being acted on, ensuring getEditorIntegration(...) operates on the correct editor type.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/browser/chatEditing/chatEditingActions.ts	Ensures “Open Changes in Diff Editor” opens the target file editor pane (not an unrelated active webview) before toggling diff.

Copilot's findings

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• Comments generated: 0