Fix prefer-lowest CI build by using composer update

The --prefer-lowest flag only works with 'composer update', not 'composer install'.
Split the install step into two conditional steps:
- Regular install for stable builds
- Update with --prefer-lowest for lowest dependency builds

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

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

Author: Thavarshan

.github/workflows/ci.yml

@@ -114,7 +114,12 @@ jobs:
             ${{ runner.os }}-php${{ matrix.php }}-composer-
 
       - name: Install dependencies
-        run: composer install --no-interaction --prefer-dist --optimize-autoloader ${{ matrix.stability == 'prefer-lowest' && '--prefer-lowest' || '' }} ${{ matrix.os == 'windows-latest' && '--ignore-platform-req=ext-pcntl' || '' }}
+        if: matrix.stability != 'prefer-lowest'
+        run: composer install --no-interaction --prefer-dist --optimize-autoloader ${{ matrix.os == 'windows-latest' && '--ignore-platform-req=ext-pcntl' || '' }}
+
+      - name: Install dependencies (prefer-lowest)
+        if: matrix.stability == 'prefer-lowest'
+        run: composer update --no-interaction --prefer-dist --optimize-autoloader --prefer-lowest ${{ matrix.os == 'windows-latest' && '--ignore-platform-req=ext-pcntl' || '' }}
 
       - name: Execute tests
         run: composer test