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/hooks/atCommandProcessor.ts

@@ -154,7 +154,9 @@ export async function handleAtCommand({
     if (isNodeError(error) && error.code === 'ENOENT') {
       onDebugMessage(`Path not found, proceeding with original: ${pathSpec}`);
     } else {
-      console.error(`Error stating path ${pathPart}:`, error);
+      console.error(
+        `Error stating path ${pathPart}: ${getErrorMessage(error)}`,
+      );
       onDebugMessage(
         `Error stating path, proceeding with original: ${pathSpec}`,
       );
@@ -200,7 +202,7 @@ export async function handleAtCommand({
     );
 
     return { processedQuery, shouldProceed: true };
-  } catch (error) {
+  } catch (error: unknown) {
     // Handle errors during tool execution
     toolCallDisplay = {
       callId: `client-read-${userMessageTimestamp}`,