fix: Ensure filename is available for diff rendering in write-file

This commit resolves a bug where the `write-file` operation could fail to render content due to a missing filename.

The fix involves:
- Ensuring `fileName` is consistently passed to `DiffRenderer.tsx` through `ToolConfirmationMessage.tsx`, `ToolMessage.tsx`, and `useGeminiStream.ts`.
- Modifying `edit.ts` and `write-file.ts` to include `fileName` in the `FileDiff` object.
- Expanding the `FileDiff` interface in `tools.ts` to include `fileName`.

Additionally, this commit enhances the diff rendering by:
- Adding syntax highlighting based on file extension in `DiffRenderer.tsx`.
- Adding more language mappings to `getLanguageFromExtension` in `DiffRenderer.tsx`.
- Added lots of tests for all the above.

Fixes https://b.corp.google.com/issues/418125982

packages/cli/src/ui/components/messages/ToolConfirmationMessage.tsx

@@ -52,7 +52,12 @@ export const ToolConfirmationMessage: React.FC<
   if (isEditDetails(confirmationDetails)) {
     // Body content is now the DiffRenderer, passing filename to it
     // The bordered box is removed from here and handled within DiffRenderer
-    bodyContent = <DiffRenderer diffContent={confirmationDetails.fileDiff} />;
+    bodyContent = (
+      <DiffRenderer
+        diffContent={confirmationDetails.fileDiff}
+        filename={confirmationDetails.fileName}
+      />
+    );
 
     question = `Apply this change?`;
     options.push(