ci(site): add format/lint/test/build workflow for astro site

Add Site GitHub Actions workflow running prettier format check, astro
check, tests, and build on changes under site/. Wire prettier into the
site package with config, ignore, and scripts, and format existing
sources.

site/package-lock.json

@@ -14,6 +14,8 @@
       "devDependencies": {
         "@astrojs/check": "^0.9.9",
         "@tailwindcss/vite": "^4.0.0",
+        "prettier": "3.8.3",
+        "prettier-plugin-astro": "0.14.1",
         "tailwindcss": "^4.0.0",
         "typescript": "^5.6.0"
       }
@@ -5717,6 +5719,21 @@
         "url": "https://github.com/prettier/prettier?sponsor=1"
       }
     },
+    "node_modules/prettier-plugin-astro": {
+      "version": "0.14.1",
+      "resolved": "https://registry.npmjs.org/prettier-plugin-astro/-/prettier-plugin-astro-0.14.1.tgz",
+      "integrity": "sha512-RiBETaaP9veVstE4vUwSIcdATj6dKmXljouXc/DDNwBSPTp8FRkLGDSGFClKsAFeeg+13SB0Z1JZvbD76bigJw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@astrojs/compiler": "^2.9.1",
+        "prettier": "^3.0.0",
+        "sass-formatter": "^0.7.6"
+      },
+      "engines": {
+        "node": "^14.15.0 || >=16.0.0"
+      }
+    },
     "node_modules/prismjs": {
       "version": "1.30.0",
       "resolved": "https://registry.npmjs.org/prismjs/-/prismjs-1.30.0.tgz",
@@ -6066,6 +6083,23 @@
         "fsevents": "~2.3.2"
       }
     },
+    "node_modules/s.color": {
+      "version": "0.0.15",
+      "resolved": "https://registry.npmjs.org/s.color/-/s.color-0.0.15.tgz",
+      "integrity": "sha512-AUNrbEUHeKY8XsYr/DYpl+qk5+aM+DChopnWOPEzn8YKzOhv4l2zH6LzZms3tOZP3wwdOyc0RmTciyi46HLIuA==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/sass-formatter": {
+      "version": "0.7.9",
+      "resolved": "https://registry.npmjs.org/sass-formatter/-/sass-formatter-0.7.9.tgz",
+      "integrity": "sha512-CWZ8XiSim+fJVG0cFLStwDvft1VI7uvXdCNJYXhDvowiv+DsbD1nXLiQ4zrE5UBvj5DWZJ93cwN0NX5PMsr1Pw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "suf-log": "^2.5.3"
+      }
+    },
     "node_modules/sax": {
       "version": "1.6.0",
       "resolved": "https://registry.npmjs.org/sax/-/sax-1.6.0.tgz",
@@ -6256,6 +6290,16 @@
         "url": "https://github.com/chalk/strip-ansi?sponsor=1"
       }
     },
+    "node_modules/suf-log": {
+      "version": "2.5.3",
+      "resolved": "https://registry.npmjs.org/suf-log/-/suf-log-2.5.3.tgz",
+      "integrity": "sha512-KvC8OPjzdNOe+xQ4XWJV2whQA0aM1kGVczMQ8+dStAO6KfEB140JEVQ9dE76ONZ0/Ylf67ni4tILPJB41U0eow==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "s.color": "0.0.15"
+      }
+    },
     "node_modules/svgo": {
       "version": "4.0.1",
       "resolved": "https://registry.npmjs.org/svgo/-/svgo-4.0.1.tgz",