Addresses 16 review findings across two passes:
- Clarify _active.pop/double-decrement non-issue
- Fix app.py change target (inline SQL, not kill_stuck_tasks)
- Scope durability to LLM types only
- Add _budgets to state table with load logic
- Fix singleton safety explanation (lock, not GIL)
- Ghost row fix: mark dropped tasks failed in DB
- Document static _available_vram as known limitation
- Fix test_llm_tasks_batch_by_type description
- Eliminate circular import via routing split in submit_task()
- Add missing budget warning at construction
