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

package-lock.json

@@ -4477,6 +4477,24 @@
         "react": ">=18.0.0"
       }
     },
+    "node_modules/ink-testing-library": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/ink-testing-library/-/ink-testing-library-4.0.0.tgz",
+      "integrity": "sha512-yF92kj3pmBvk7oKbSq5vEALO//o7Z9Ck/OaLNlkzXNeYdwfpxMQkSowGTFUCS5MSu9bWfSZMewGpp7bFc66D7Q==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      },
+      "peerDependencies": {
+        "@types/react": ">=18.0.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/react": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/ink-text-input": {
       "version": "6.0.0",
       "resolved": "https://registry.npmjs.org/ink-text-input/-/ink-text-input-6.0.0.tgz",
@@ -8156,6 +8174,7 @@
         "@types/react": "^18.3.1",
         "@types/shell-quote": "^1.7.5",
         "@types/yargs": "^17.0.32",
+        "ink-testing-library": "^4.0.0",
         "jsdom": "^26.1.0",
         "typescript": "^5.3.3",
         "vitest": "^3.1.1"