Summary

• Consolidate _is_no_request(), _is_idle_for_hicache_storage_op(), and inline health-check logic into a single is_fully_idle(for_health_check=False)
• Tighten release_memory_occupation and flush_cache guards to use is_fully_idle() — now also checks chunked_req, dllm_manager, waiting_queue, and grammar_queue

Background

• Old _is_no_request() did not check waiting_queue or grammar_queue, so flush_cache could clear KV cache while retracted requests sat in waiting_queue
• Old _is_idle_for_hicache_storage_op() was a superset of _is_no_request() but missed chunked_req and dllm_manager
• Health-check skip logic was inlined with ~25 lines of ad-hoc checks duplicating the above

Fix

• is_fully_idle() covers all batch-running state (including chunked_req, dllm_manager, overlap, PP, disagg) plus all waiting queues
• for_health_check=True skips grammar queue and prefill inflight queue (they don't produce immediate batch results, so ongoing requests in other queues already carry health info)
• release_memory_occupation now asserts is_fully_idle() instead of _is_no_request()
• Fix test_update_weights to use pause_generation("abort") which fully drains all requests before weight update (old "retract" mode left requests in waiting_queue, incompatible with the stricter idle check)
• Update hicache docs to reference is_fully_idle()