ci: enable pcov coverage driver

phpunit.xml.dist requests a coverage report but the workflow set
`coverage: none`, producing a "No code coverage driver available"
warning that combined with `failOnWarning="true"` failed the build.
pcov is the lightweight driver appropriate for CI coverage capture.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nficano

.github/workflows/test.yml

@@ -51,7 +51,7 @@ jobs:
         with:
           php-version: ${{ matrix.php }}
           extensions: pdo, pdo_sqlite, mbstring, json
-          coverage: none
+          coverage: pcov
           tools: composer:v2
 
       - name: Get composer cache directory