[WIP] Add zkTLS airdrop example

[critesjosh]

Summary

• Adds zktls-airdrop/ example: fully-private token airdrop on Aztec using Primus zkTLS attestations to verify GitHub contributors
• PrimusAirdrop contract verifies ECDSA-signed zkTLS attestations, prevents double-claims via nullifiers, and mints private tokens cross-contract via defi-wonderland/aztec-standards Token
• Includes attestation generation, parsing, deployment scripts, benchmark tooling, and integration tests
• Updates root .gitignore for .env, generated artifacts (store, artifacts, codegenCache.json, *.json.bak)
• Adds .env.example with placeholder Primus API credentials
• Updates root CLAUDE.md project structure

Test plan

• cd zktls-airdrop && yarn install
• yarn ccc compiles contract and generates TypeScript bindings
• aztec start --local-network starts local network
• yarn test runs integration tests (deploy + set_token + claim + double-claim rejection)
• yarn claim deploys contracts and submits a claim with a valid attestation
• yarn benchmark profiles gate counts for all contract operations
• Verify .env is not tracked by git
• Verify contract/target/, contract/artifacts/, node_modules/ are excluded

🤖 Generated with Claude Code