test: add Playwright smoke suite (cookie banner, lang switcher, FamilyAtlas, WritingIssue)

34 tests across desktop + mobile (Chromium/Pixel 5). Verifies all client-side
React islands and interactive features that astro build/WebFetch cannot confirm.
API-dependent WritingIssue shows graceful error against local preview; resolves
on the live site where the PHP backend is available.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package-lock.json

@@ -16,6 +16,7 @@
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       },
       "devDependencies": {
+        "@playwright/test": "^1.60.0",
         "@resvg/resvg-js": "^2.6.2",
         "satori": "^0.26.0"
       },
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       "license": "MIT"
     },
+    "node_modules/@playwright/test": {
+      "version": "1.60.0",
+      "resolved": "https://registry.npmjs.org/@playwright/test/-/test-1.60.0.tgz",
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+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
+        "playwright": "1.60.0"
+      },
+      "bin": {
+        "playwright": "cli.js"
+      },
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@@ -4587,6 +4604,53 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
+    "node_modules/playwright": {
+      "version": "1.60.0",
+      "resolved": "https://registry.npmjs.org/playwright/-/playwright-1.60.0.tgz",
+      "integrity": "sha512-hheHdokM8cdqCb0lcE3s+zT4t4W+vvjpGxsZlDnikarzx8tSzMebh3UiFtgqwFwnTnjYQcsyMF8ei2mCO/tpeA==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
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+      },
+      "bin": {
+        "playwright": "cli.js"
+      },
+      "engines": {
+        "node": ">=18"
+      },
+      "optionalDependencies": {
+        "fsevents": "2.3.2"
+      }
+    },
+    "node_modules/playwright-core": {
+      "version": "1.60.0",
+      "resolved": "https://registry.npmjs.org/playwright-core/-/playwright-core-1.60.0.tgz",
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+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "playwright-core": "cli.js"
+      },
+      "engines": {
+        "node": ">=18"
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+      "dev": true,
+      "hasInstallScript": true,
+      "license": "MIT",
+      "optional": true,
+      "os": [
+        "darwin"
+      ],
+      "engines": {
+        "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
+      }
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     "node_modules/postcss": {
       "version": "8.5.8",
       "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.8.tgz",