fix(eip712): harden typed-data signing correctness (odd-length hex + primaryType inference)

[Nexory]

What

Two correctness fixes in the EIP-712 typed-data signing path.

Why

1. util/eip712.ts - an odd-length hex value is silently truncated

hexToBytes allocates new Uint8Array(clean.length / 2), which floors a fractional length. An odd-length hex string therefore drops its last nibble, and encodeValue for a bytes value then hashes the truncated data - the adapter signs the wrong content with no error.

2. bridges/ethers.ts - wrong primaryType when it is omitted

When signTypedData is called without an explicit primaryType, the bridge used Object.keys(types).find(t => t !== "EIP712Domain"), i.e. the first key. EIP-712's primary type is the struct that is not referenced as a field type by any other struct (the root of the type graph), which is what ethers.js infers. When the root is not declared first (for example a dependency struct is listed above it), the bridge signs the wrong struct.

Change

• hexToBytes rejects an odd-length hex string instead of truncating it.
• The ethers bridge infers the root type (the struct not referenced by any other) when primaryType is omitted.

Tests

Adds one regression test per fix. Against the current code both fail:

hashTypedData > rejects an odd-length hex bytes value instead of silently truncating
  AssertionError: expected [Function] to throw an error

EthersAdapterSigner > infers the root primaryType when omitted, not the first types key
  expected "spy" to be called with { primaryType: "Mail" }, received "Person"

With the fixes both pass and the full suite stays green:

Test Files  4 passed (4)
      Tests  72 passed (72)