feat(merkle-tree-token-claimer): add pinocchio example - #714

Adds a Pinocchio implementation of merkle-tree-token-claimer, alongside the existing Anchor one.

What it does

The airdrop pattern: fund a vault once, publish a Merkle root of the balance snapshot, and let each holder claim their allocation by proving membership.

Three instructions:

• InitializeAirdropData — creates the mint, mints the whole supply into a vault owned by the airdrop PDA, records the root, then revokes the mint authority so the supply is fixed at what the vault holds.
• UpdateTree — replaces the root, allowed only before the first claim.
• ClaimAirdrop — verifies a proof, pays the claimant, and writes a receipt so the index cannot be claimed twice.

Proof verification

The leaf is claimer (32) | amount (8 LE), sha256-hashed; internal nodes are sha256(left || right); index doubles as the path, its low bit choosing the side at each level. Two properties are worth calling out because both are load-bearing and neither is obvious:

• The leaf commits to the claimer, so a proof lifted from someone else's claim recomputes a different root. Tested.
• index must be zero after the walk. The loop only consumes as many index bits as the proof has levels, so without the trailing check the same proof would also open receipt PDAs at index + 2^depth, index + 2^(depth+1), … — one leaf, many payouts. Tested with an aliased index.

The suite reuses the Anchor version's tests/merkle.ts verbatim, so both implementations are checked against the same tree builder — including its zero-hash padding for odd levels (duplicating the last node instead would make a parent sha256(C || C), which verifies at two indices). The test tree has three leaves specifically to exercise that padding.

Hashing uses solana-sha256-hasher, which compiles to the sol_sha256 syscall on SBF; it is added to the workspace dependencies here.

Differences from the Anchor version

• Instruction data puts the proof last: [amount, index, hashes…], with the proof length implied by the remaining bytes, rather than a Borsh Vec<u8> in the middle.
• No 8-byte account discriminators, so the state is 113 bytes and each receipt 81.
• The receipt account is created only after the proof verifies, so a bad proof costs the caller nothing and leaves no account behind. Anchor's init_if_needed creates it first and then rolls back.

One ordering note for reviewers: the already-claimed check runs before proof verification, so replaying a proof at an already claimed index reports AlreadyClaimed rather than InvalidProof. The test for proof binding therefore uses an unclaimed index.

Tests

9 LiteSVM tests: the full lifecycle through to a drained vault, plus repeat-claim, stolen-proof, aliased-index, non-authority update and post-claim update rejections. Verified locally: tsc --noEmit, pnpm test, prettier --check, cargo fmt --check, cargo clippy -D warnings.