stop-hook-infinite-loop-during-brainstorming-await

The session-stop hook repeatedly fires (~30+ times) when the agent is mid-brainstorming workflow awaiting user input between design sections, creating an infinite hold-acknowledge loop with no progress. Root cause: hook blocks on ‘structural completeness’ even for pure planning sessions with zero file modifications. Fix: the stop hook should APPROVE pure planning sessions unconditionally; structural completeness checks should not override the no-modifications APPROVE criterion.