fix(release): replace \s with [[:space:]] in bump sed (BSD compat)

Critical: macOS BSD sed does not support \s character class.
The two substitutions in the version-bump step silently no-oped, the
grep fail-fast guard caught it (no remote damage), but release.sh
couldn't complete. Using POSIX [[:space:]] works on both BSD and GNU sed.

Also: extend test_git_archive_excludes_dev_files to cover .phpunit.result.cache,
.beads/, .claude/, dist/, .DS_Store — the test now fully enforces .gitattributes
export-ignore invariant.

release.sh

@@ -76,8 +76,8 @@ log "Validation passed: version=$VERSION, tag=$TAG, branch=$BRANCH"
 log "Bumping version to $VERSION in cf7-spam-to-telegram.php and readme.txt"
 
 sed -i.bak -E \
-    -e "s|^(\\s*\\*\\s*Version:\\s*).*$|\\1${VERSION}|" \
-    -e "s|define\\('CF7STG_VERSION',\\s*'[^']+'\\)|define('CF7STG_VERSION', '${VERSION}')|" \
+    -e "s|^([[:space:]]*\\*[[:space:]]*Version:[[:space:]]*).*$|\\1${VERSION}|" \
+    -e "s|define\\('CF7STG_VERSION',[[:space:]]*'[^']+'\\)|define('CF7STG_VERSION', '${VERSION}')|" \
     cf7-spam-to-telegram.php
 rm cf7-spam-to-telegram.php.bak