Pass the Parcel: a Uniswap v4 hook on a native ETH pool. Every sell adds 1% of its ETH output to a pot held by the hook for that pool; the next qualifying buy in the same pool receives that pool's whole pot inside its own swap.

Token: ERC-20, name "Parcel", symbol "PRCL", 18 decimals. The zero argument constructor mints exactly 10^27 minor units to msg.sender (the launch factory) and nothing else, ever. No owner, mint, pause, proxy, fees or hooks on transfer.

Hook:

• Constructor takes only the PoolManager address. No owner, admin, setters, pause, sweep or upgrade. Does not use beforeInitialize; the factory opens the pool.
• Pots are kept per pool, keyed by PoolId. A swap in one pool can never add to or take from another pool's pot. On any pool whose currency0 is not native ETH, the hook does nothing.
• Sell (PRCL in, ETH out): the hook takes exactly 1% of the ETH the seller would receive and adds it to that pool's pot. Works for exact input and exact output swaps.
• Buy (ETH in, PRCL out) with at least 0.001 ETH of input: the hook pays that pool's pot to the buyer by reducing the ETH the buyer owes in that same swap. If the pot is larger than the buyer's ETH input, pay only up to the input and keep the rest in the pot. Buys under 0.001 ETH leave the pot untouched.
• The hook never pays anyone outside a swap. A pot can only leave through a qualifying buy in its own pool.
• View pot(PoolId) returns a pool's current pot in wei. Events: ParcelFilled(PoolId indexed poolId, uint256 added, uint256 potAfter) on every sell, ParcelPassed(PoolId indexed poolId, uint256 paid, uint256 potAfter) on every payout.
• Tests: exact input and exact output in both directions against a hookless reference pool; the pot rises by exactly 1% of each sell's ETH; a buy under 0.001 ETH does not touch the pot; a buy smaller than the pot takes only its own input; a second pool using the same hook with a different token cannot take the first pool's pot; a pool not paired with native ETH is left untouched; invariant: the hook's ETH held always equals the sum of all pots; fuzz swap sizes; the constructor rejects the zero PoolManager and mismatched permission bits.