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

1 files changed, 4 insertions, 1 deletions

diff --git a/packages/cli/src/ui/components/messages/ToolMessage.tsx b/packages/cli/src/ui/components/messages/ToolMessage.tsx
index 091785f2..32b23b9e 100644
--- a/packages/cli/src/ui/components/messages/ToolMessage.tsx
+++ b/packages/cli/src/ui/components/messages/ToolMessage.tsx
@@ -90,7 +90,10 @@ export const ToolMessage: React.FC<ToolMessageProps> = ({
               </Box>
             )}
             {typeof displayableResult === 'object' && (
-              <DiffRenderer diffContent={displayableResult.fileDiff} />
+              <DiffRenderer
+                diffContent={displayableResult.fileDiff}
+                filename={displayableResult.fileName}
+              />
             )}
             {hiddenLines > 0 && (
               <Box>