gnomic_airdrop package

Claim-based airdrop realm with Merkle proofs.

Why Merkle rather than an on-chain list:

• the beneficiary list can run to tens of thousands of rows; writing it on-chain costs gas and storage deposit in proportion;
• here only 32 bytes go on-chain (the root), plus one record per ACTUAL claim. Whoever never claims costs nothing.

Operating flow:

1. deploy this realm;
2. fund it by transferring GRC20 tokens to it (its address is returned by RealmAddress());
3. the admin publishes root, leaf count and deadline block with SetCampaign;
4. each beneficiary calls Claim with their own proof;
5. after the deadline the admin recovers the residue with Sweep.

The Merkle leaf is the string "<address>|<amount in base units>", UTF-8 encoded. The tree is Tendermint's "simple tree" (gno's crypto/merkle): leaf = SHA256(0x00||data), node = SHA256(0x01||left||right), split at the largest power of two below n. The generator in tools/merkle produces compatible proofs.