ERC-4626 Vault Comparator

Reads convertToAssets for exactly one share now and at a past block, so the yield is derived from how the share price genuinely moved. Compares several vaults side by side and annualises the result, while warning that annualising a short window magnifies noise — a week containing a large harvest projects an APY the vault cannot sustain. Flags a falling share price prominently, since in a working vault it should only ever rise: a fall means depositors lost principal. Needs an RPC serving historical state; without it no past share price can be read and the app says so rather than showing a made-up yield. Annualising a short window magnifies noise badly, so a week that happened to include a large harvest will project a return the vault cannot sustain.