Add Playwright E2E harness for the RDM audit workspace

Why: U4 acceptance requires real-browser runs of the trace/audit
workspace; the repo had only a manual .playwright.ts stub gated on
PLAYWRIGHT_BASE_URL with no config, deps, or service wiring.

Evidence: config/deps/spec staged; full run driven by Dev-side
scripts/e2e.sh (seed-only smoke in progress in this task branch).

Impact: dev-only additions (@playwright/test devDep, preview proxy
segment, e2e/rdm-audit.playwright.ts); no production bundle changes.

Refs: Dev task feature/rdm-e2e-acceptance; U4 in
modules/documents/docs/proposals/2026-10-11-rdm-two-trees-trace-audit-integration.md

package-lock.json

@@ -19,6 +19,7 @@
         "xlsx": "^0.18.5"
       },
       "devDependencies": {
+        "@playwright/test": "^1.50.1",
         "@types/node": "^22.20.4",
         "@types/react": "^19.2.0",
         "@types/react-dom": "^19.2.0",
@@ -1212,6 +1213,22 @@
         "win32"
       ]
     },
+    "node_modules/@playwright/test": {
+      "version": "1.64.0",
+      "resolved": "https://registry.npmjs.org/@playwright/test/-/test-1.64.0.tgz",
+      "integrity": "sha512-oTN9FNYuN6bqQMwiho6jJKLCG2/QOYCixGXuCjRmzOq23eODeukuY2XiAVoVpAECbuezMt1MHQjAiQxK8F+Y+g==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
+        "playwright": "1.64.0"
+      },
+      "bin": {
+        "playwright": "cli.js"
+      },
+      "engines": {
+        "node": ">=20"
+      }
+    },
     "node_modules/@rolldown/pluginutils": {
       "version": "1.0.0-beta.27",
       "resolved": "https://registry.npmjs.org/@rolldown/pluginutils/-/pluginutils-1.0.0-beta.27.tgz",
@@ -2749,6 +2766,35 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
+    "node_modules/playwright": {
+      "version": "1.64.0",
+      "resolved": "https://registry.npmjs.org/playwright/-/playwright-1.64.0.tgz",
+      "integrity": "sha512-kVzTnYFYEyQ9RGzBjNCd2+yEqWmVbxl3AHPynv3qQ6JTjv4a+kwRcnqQwIpuP3NnrnIrE/Q6wWAIAvMfIE2/Yg==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
+        "playwright-core": "1.64.0"
+      },
+      "bin": {
+        "playwright": "cli.js"
+      },
+      "engines": {
+        "node": ">=20"
+      }
+    },
+    "node_modules/playwright-core": {
+      "version": "1.64.0",
+      "resolved": "https://registry.npmjs.org/playwright-core/-/playwright-core-1.64.0.tgz",
+      "integrity": "sha512-T9r+MZkTECl2+oUcZ26YgZzTrYidTsIhYYkJix+6iDOymOb1FB2RLLSOxRGnZGv5DStt+aduIVbt+E8WygXYpg==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "playwright-core": "cli.js"
+      },
+      "engines": {
+        "node": ">=20"
+      }
+    },
     "node_modules/postcss": {
       "version": "8.5.28",
       "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.28.tgz",