fix(ci): drop the bad gh-mirror/ rsync exclude (it blocked --delete cleanup)

rsync's --exclude also protects the matching path at the DESTINATION from
--delete. The belt-and-suspenders --exclude='gh-mirror/' I added in the previous
fix prevented the stray gh-mirror/ subtree at the destination from ever being
deleted by --delete, defeating the auto-heal. The structural fix (cloning the
GitHub mirror into $RUNNER_TEMP, outside ./) already prevents the recursive
self-include, so the exclude is unnecessary and harmful. Removed it; left an
explanatory NOTE in the workflow so this isn't re-added.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TfzV5QvtPDz8LJS3Pu5VLT

.gitea/workflows/sync-github-mirror.yml

@@ -53,14 +53,16 @@ jobs:
           # Mirror this checkout's tree into gh-mirror/ with the exclusions.
           # --delete drops files removed on the source; --exclude='.git' protects
           # both repos' .git dirs from rsync touching them.
-          # belt-and-suspenders exclude of the clone dir name in case anyone re-uses ./gh-mirror.
+          # NOTE: do NOT add an --exclude for the clone target dir name; rsync's --exclude also
+          # protects the matching path at the DESTINATION from --delete, which would prevent
+          # any stray copy of that dir from ever being cleaned up. The clone living in
+          # $RUNNER_TEMP (outside ./) already prevents the recursive self-include.
           rsync -a --delete \
             --exclude='.git' \
             --exclude='.gitea/' \
             --exclude='.claude/' \
             --exclude='blog/' \
             --exclude='handoff.md' \
-            --exclude='gh-mirror/' \
             --exclude='__pycache__/' \
             --exclude='*.pyc' \
             --exclude='tasks.json' \