feat: if byteLength !== 32 then base64 decode anchor

[PeterFarber]

Fix anchor decoding in calcDataItemDeepHash

Problem

The calcDataItemDeepHash function was not handling anchors that come encoded as base64url strings. The createData function from warp-arbundles requires anchors to be exactly 32 bytes, but when anchors are provided as base64url-encoded strings (44 characters), they need to be decoded first before being passed to createData.

Without this fix, messages with base64url-encoded anchors would fail validation with the error: "Anchor must be 32 bytes".

Solution

Added logic to detect and decode base64url-encoded anchors before passing them to createData:

• If the anchor is a string and NOT 32 bytes: Decode it from base64url format to get the 32-byte buffer
• If the anchor is already 32 bytes (or null/undefined): Use it as-is

Changes

• Modified calcDataItemDeepHash function in hydrateMessages.js
• Added check: Buffer.byteLength(anchor, 'utf8') !== 32
• Decode using: Buffer.from(anchor, 'base64url') when needed

Example

Before this fix, an anchor like "MDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDMwNTQzOTg" (base64url-encoded) would fail. After this fix:

• It's detected as 44 bytes (not 32)
• Decoded to: "00000000000000000000000003054398" (32 bytes)
• Successfully passed to createData