feat(argon2): vendor hash-wasm v4.12.0 as @bitgo/argon2

[pranavjain97]

Vendor the argon2 subset of hash-wasm as a new @bitgo/argon2 module, following the same pattern as @bitgo/sjcl. The pre-built UMD bundle (~29KB) contains argon2 and blake2b WASM binaries embedded as base64 with zero runtime dependencies.

Exports: argon2id, argon2i, argon2d, argon2Verify with full TypeScript type definitions. Includes verify-vendor.sh script for reproducible re-vendoring from npm.

This module is a prerequisite for migrating BitGoJS encryption from SJCL (PBKDF2-SHA256 @ 10k iterations, ~1ms per guess on modern hardware) to Argon2id, which is memory-hard and GPU-resistant.

TICKET: WCN-29

[linear]

WCN-29 Vendor hash-wasm into BitGoJS

[sachushaji]

@claude

[zahin-mohammad]

Review: Supply Chain, Auditability & Release Risks

The vendoring approach (following @bitgo/sjcl precedent) is sound in principle, and the motivation — migrating from PBKDF2-SHA256 to Argon2id — is the right move. However, there are gaps that should be addressed before merging, given this is cryptographic code in a financial SDK.

Supply Chain Risk (HIGH)

• The vendored bundle contains opaque base64-encoded WASM binaries that cannot be reviewed from the diff. Trust is anchored entirely to an npm tarball from a single maintainer.
• verify-vendor.sh verifies against npm, not against a reproducible source build. A compromised npm publish would pass verification. Pin the expected SHA256 and trace provenance to a specific git commit.

Auditability (HIGH)

• No RFC 9106 known-answer test vectors. The test suite verifies behavioral properties but never asserts exact output against published reference vectors. A subtly broken or backdoored WASM implementation would pass all current tests. This is the single most important gap to close.
• Hand-written index.d.ts with "include": [] in tsconfig means types are never validated against the JS exports.

Release Integration (MEDIUM)

• "private": true will block npm publish if downstream packages depend on this.
• Missing standard monorepo scripts (build, test, lint, clean), no ESM support, not added to root workspaces.
• Buffer type in index.d.ts without @types/node dependency breaks browser-only TS consumers.

See inline comments for specifics on each file.