Fix Docker build by splitting client-safe gua utils from fs-based content loader.

Client components were importing zhouyi.ts which pulled in fs/promises; move pure helpers to gua-utils.ts and mark zhouyi.ts server-only.

Co-authored-by: Cursor <cursoragent@cursor.com>

package-lock.json

@@ -22,6 +22,7 @@
         "react": "^18.3.1",
         "react-dom": "^18.3.1",
         "react-markdown": "^9.0.3",
+        "server-only": "^0.0.1",
         "tailwind-merge": "^2.6.0"
       },
       "devDependencies": {
@@ -7369,6 +7370,12 @@
         "node": ">=10"
       }
     },
+    "node_modules/server-only": {
+      "version": "0.0.1",
+      "resolved": "https://registry.npmmirror.com/server-only/-/server-only-0.0.1.tgz",
+      "integrity": "sha512-qepMx2JxAa5jjfzxG79yPPq+8BuFToHd1hm7kI+Z4zAq1ftQiP7HcxMhDDItrbtwVeLg/cY2JnKnrcFkmiswNA==",
+      "license": "MIT"
+    },
     "node_modules/set-function-length": {
       "version": "1.2.2",
       "resolved": "https://registry.npmjs.org/set-function-length/-/set-function-length-1.2.2.tgz",