Add diff viewer to git commit dialog (#374)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src-web/package.json

@@ -14,7 +14,9 @@
     "@codemirror/lang-json": "^6.0.1",
     "@codemirror/lang-markdown": "^6.3.2",
     "@codemirror/lang-xml": "^6.1.0",
+    "@codemirror/lang-yaml": "^6.1.2",
     "@codemirror/language": "^6.11.0",
+    "@codemirror/merge": "^6.11.2",
     "@codemirror/search": "^6.5.11",
     "@dnd-kit/core": "^6.3.1",
     "@gilbarbara/deep-equal": "^0.3.1",