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

.github/workflows/ci.yml

@@ -38,12 +38,12 @@ jobs:
       - name: Run linter
         run: npm run lint
 
-      - name: Run type check
-        run: npm run typecheck
-
       - name: Build project
         run: npm run build
 
+      - name: Run type check
+        run: npm run typecheck
+
       - name: Upload build artifacts
         uses: actions/upload-artifact@v4
         with: