fix(ci): use Node 20.16.0 in baseline allowlist workflow to match package.json engines

The baseline allowlist workflow was failing during pnpm install with:
  ERR_PNPM_UNSUPPORTED_ENGINE  Unsupported environment

Root cause: Workflow used Node 22.x but package.json requires:
- engines.node: 20.16.0
- engines.pnpm: 9

Fix: Change node-version from '22.x' to '20.16.0' in both jobs
(gen-matrix and run-allowlisted) to match package.json requirements.

This allows corepack to install the correct pnpm version (9.x)
and dependencies to install successfully.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: mirqtio

.github/workflows/playwright-baseline-allowlist.yml

@@ -22,7 +22,7 @@ jobs:
 
       - uses: actions/setup-node@v4
         with:
-          node-version: '22.x' # Match local Node v22.15.0
+          node-version: '20.16.0' # Match package.json engines.node
 
       - name: Install deps
         run: |
@@ -47,7 +47,7 @@ jobs:
 
       - uses: actions/setup-node@v4
         with:
-          node-version: '22.x' # Match local Node v22.15.0
+          node-version: '20.16.0' # Match package.json engines.node
 
       - name: Install browsers (Playwright)
         run: |