Add syntax highlighting for git diffs

package-lock.json

@@ -16,6 +16,7 @@
         "@codemirror/lang-markdown": "^6.5.0",
         "@codemirror/lang-python": "^6.2.1",
         "@codemirror/lang-rust": "^6.0.2",
+        "@codemirror/legacy-modes": "^6.5.2",
         "@earendil-works/pi-coding-agent": "^0.74.0",
         "@fastify/static": "^8.3.0",
         "@fastify/websocket": "^11.2.0",
@@ -991,6 +992,15 @@
         "style-mod": "^4.0.0"
       }
     },
+    "node_modules/@codemirror/legacy-modes": {
+      "version": "6.5.2",
+      "resolved": "https://registry.npmjs.org/@codemirror/legacy-modes/-/legacy-modes-6.5.2.tgz",
+      "integrity": "sha512-/jJbwSTazlQEDOQw2FJ8LEEKVS72pU0lx6oM54kGpL8t/NJ2Jda3CZ4pcltiKTdqYSRk3ug1B3pil1gsjA6+8Q==",
+      "license": "MIT",
+      "dependencies": {
+        "@codemirror/language": "^6.0.0"
+      }
+    },
     "node_modules/@codemirror/lint": {
       "version": "6.9.6",
       "resolved": "https://registry.npmjs.org/@codemirror/lint/-/lint-6.9.6.tgz",