feat(web): add markdown syntax highlighting, slash commands, stop button, quote/reply

- PromptEditor with Prism.js syntax highlighting
- Slash commands (/run, /status, /images, /list, /help) in chat input
- Stop button to cancel ongoing generation
- Quote/reply and regenerate/continue actions in chat
- MiddlePanel with conversation timestamps and preview
- Pipeline progress in chat view
- Fix all remaining dark theme classes

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/client/package-lock.json

@@ -12,14 +12,17 @@
         "clsx": "^2.1.0",
         "lucide-react": "^0.460.0",
         "markdown-it": "^14.1.0",
+        "prismjs": "^1.30.0",
         "react": "^18.3.0",
         "react-dom": "^18.3.0",
         "react-router-dom": "^7.15.0",
+        "react-simple-code-editor": "^0.14.1",
         "tailwind-merge": "^2.6.0",
         "zustand": "^5.0.0"
       },
       "devDependencies": {
         "@types/markdown-it": "^14.1.0",
+        "@types/prismjs": "^1.26.6",
         "@types/react": "^18.3.0",
         "@types/react-dom": "^18.3.0",
         "@types/react-router-dom": "^5.3.3",
@@ -1246,6 +1249,13 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@types/prismjs": {
+      "version": "1.26.6",
+      "resolved": "https://registry.npmjs.org/@types/prismjs/-/prismjs-1.26.6.tgz",
+      "integrity": "sha512-vqlvI7qlMvcCBbVe0AKAb4f97//Hy0EBTaiW8AalRnG/xAN5zOiWWyrNqNXeq8+KAuvRewjCVY1+IPxk4RdNYw==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/prop-types": {
       "version": "15.7.15",
       "resolved": "https://registry.npmjs.org/@types/prop-types/-/prop-types-15.7.15.tgz",
@@ -2336,6 +2346,15 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/prismjs": {
+      "version": "1.30.0",
+      "resolved": "https://registry.npmjs.org/prismjs/-/prismjs-1.30.0.tgz",
+      "integrity": "sha512-DEvV2ZF2r2/63V+tK8hQvrR2ZGn10srHbXviTlcv7Kpzw8jWiNTqbVgjO3IY8RxrrOUF8VPMQQFysYYYv0YZxw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=6"
+      }
+    },
     "node_modules/punycode.js": {
       "version": "2.3.1",
       "resolved": "https://registry.npmjs.org/punycode.js/-/punycode.js-2.3.1.tgz",
@@ -2439,6 +2458,16 @@
         "react-dom": ">=18"
       }
     },
+    "node_modules/react-simple-code-editor": {
+      "version": "0.14.1",
+      "resolved": "https://registry.npmjs.org/react-simple-code-editor/-/react-simple-code-editor-0.14.1.tgz",
+      "integrity": "sha512-BR5DtNRy+AswWJECyA17qhUDvrrCZ6zXOCfkQY5zSmb96BVUbpVAv03WpcjcwtCwiLbIANx3gebHOcXYn1EHow==",
+      "license": "MIT",
+      "peerDependencies": {
+        "react": ">=16.8.0",
+        "react-dom": ">=16.8.0"
+      }
+    },
     "node_modules/read-cache": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/read-cache/-/read-cache-1.0.0.tgz",