[BUGFIX] Add extension symlink step to CI workflow

The .Build/ directory is gitignored, so the symlink at
.Build/public/typo3conf/ext/extension_builder was never created in CI.
Unit tests resolve fixture files via Environment::getPublicPath() through
this symlink, causing all PrinterTest assertions to fail with
"file not found".

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: PKuhlmay

.github/workflows/tests.yml

@@ -41,6 +41,9 @@ jobs:
       - name: "Install dependencies"
         run: composer require "typo3/minimal:${{ matrix.typo3 }}" --prefer-dist --no-progress --no-interaction
 
+      - name: "Create extension symlink"
+        run: mkdir -p .Build/public/typo3conf/ext/ && ln -s $PWD .Build/public/typo3conf/ext/extension_builder
+
       - name: "Check PHP syntax errors"
         run: find . -name \*.php ! -path "./.Build/*" -print0 | xargs -0 -n1 -P4 php -d display_errors=stderr -n -l > /dev/null