ci: Always rebase Renovate branches to prevent stale branch deadlock

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: matthewelwell

renovate.json

@@ -5,6 +5,7 @@
     ":semanticCommitTypeAll(deps)"
   ],
   "recreateClosed": true,
+  "rebaseWhen": "always",
   "packageRules": [
     {
       "matchManagers": ["uv"],