Always clean up merged branches and scratch directories after completing a task

After merging PRs and completing a work cycle, the user consistently performs cleanup: deletes local branches (using -D for squash merges), confirms remote branches are gone, and removes temporary scratch directories (e.g., temp_*/ dirs). The user approves deletion of large scratch dirs when prompted but intentionally retains certain directories (e.g., .opencode/). The assistant should proactively identify stale local branches and temp directories at end-of-task, present a summary of what would be deleted with sizes, and wait for explicit user approval before deleting anything.