Sleeping allocation (M_WAITOK kmalloc) while holding ac_spin -> panic/deadlock

Summary

vfs_stdaccount(:158) takes ac_spin then calls unode_insert(:163)/gnode_insert(:165) which kmalloc(M_WAITOK)(:89,:103). Sleeping while holding spinlock -> panic or allocator deadlock. Same pattern in cmd_set_usage_all(:228->254/260), cmd_set_limit_uid(:298->300), cmd_set_limit_gid(:319->321). Gated by vfs_quota_enabled=0.