fix(ci): replace PCRE grep with sed for Alpine compat

Alpine Linux grep doesn't support -P (PCRE). Use sed for VERSION
and manifest version extraction.

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

.mokogitea/workflows/ci-joomla.yml

@@ -277,7 +277,7 @@ jobs:
           ERRORS=0
 
           # Extract version from README.md (supports both FILE INFORMATION block and HTML comment format)
-          README_VERSION=$(grep -oP 'VERSION:\s*\K[0-9]{2}\.[0-9]{2}\.[0-9]{2}' README.md | head -1)
+          README_VERSION=$(sed -n 's/.*VERSION:\s*\([0-9]\{2\}\.[0-9]\{2\}\.[0-9]\{2\}\).*/\1/p' README.md | head -1)
           if [ -z "$README_VERSION" ]; then
             echo "No VERSION found in README.md FILE INFORMATION block." >> $GITHUB_STEP_SUMMARY
             ERRORS=$((ERRORS + 1))
@@ -301,7 +301,7 @@ jobs:
             echo "Manifest: \`${MANIFEST}\`" >> $GITHUB_STEP_SUMMARY
 
             # Check <version> matches README VERSION
-            MANIFEST_VERSION=$(grep -oP '<version>\K[^<]+' "$MANIFEST" | head -1)
+            MANIFEST_VERSION=$(sed -n 's/.*<version>\([^<]*\)<\/version>.*/\1/p' "$MANIFEST" | head -1)
             if [ -z "$MANIFEST_VERSION" ]; then
               echo "No \`<version>\` tag in manifest." >> $GITHUB_STEP_SUMMARY
               ERRORS=$((ERRORS + 1))