cmds: allow arrays to be marked ":b64"

[jannotti]

Summary

With this change, when msgpacktool is decoding to JSON, and finds a slice that consists entirely of []bytes as the value of a string key, it will append ":b64" to the keyname, so that when msgpacktool encodes such a JSON blob, it will know to base64 decode the members of that slice.

Surprisingly, msgpacktool was already b64 encoding the slice members --- this change just makes it so that it converts them back to bytes later.

This does not change any REST APIs, but the output of a goal command that prints a block uses this change (for the better, I think).

Test Plan

[cce]

It looks like some tests in the transcode package (TestIdempotence, TestIdempotenceMultiobject) are broken from this change

[Copilot]

Pull Request Overview

Extends msgpacktool to handle arrays of byte slices by automatically appending ":b64" suffix to JSON keys when encoding, enabling proper round-trip conversion between msgpack and JSON formats for byte array data.

• Add support for detecting and marking slices of bytes with ":b64" suffix during JSON encoding
• Implement corresponding decoding logic to convert base64-encoded string arrays back to byte slices
• Update test generation to create more uniform array types for better coverage

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
protocol/transcode/core.go	Core transcoding logic with new helper functions and enhanced encoding/decoding for byte slice arrays
protocol/transcode/core_test.go	Test improvements with better error reporting and enhanced random object generation

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[cce]

LGTM — only affects msgpacktool and goal ledger block which shows a JSON block