feat: replace json with messagepack

[winton-library]

TL;DR

Replace JSON serialization with MessagePack to preserve uint64 precision in command payloads, events, and component data.

What changed?

• Switched from JSON to MessagePack for serializing command payloads, events, and component data
• Updated protobuf definitions to use bytes instead of google.protobuf.Struct for payloads
• Changed TypeSchema to use string JSON schema instead of Struct
• Added comprehensive tests to verify uint64 precision is preserved
• Added the github.com/shamaton/msgpack/v3 dependency

How to test?

Run the new test cases that verify uint64 precision:

• TestQueue_Uint64Precision in pkg/cardinal/internal/command/queue_test.go
• TestColumn_MsgpackTypeCoverage in pkg/cardinal/internal/ecs/column_internal_test.go

These tests verify that large uint64 values (above 2^53-1) maintain their precision through serialization and deserialization.

Why make this change?

JSON serialization converts uint64 values to float64, which loses precision for values larger than 2^53-1 (9007199254740991). This is problematic for game systems that rely on precise uint64 values for things like currency amounts, entity IDs, or timestamps.

MessagePack is a binary serialization format that preserves the full range of uint64 values. This change ensures that all numeric types maintain their precision throughout the serialization/deserialization process, which is critical for financial transactions and other systems requiring exact numeric representation.

[winton-library]

• feat: replace json with messagepack #867 👈 (View in Graphite)
• refactor: cardinal #865 : 2 other dependent PRs (#863 , #868 )
• main

---

How to use the Graphite Merge Queue

Add the label graphite/merge to this PR to add it to the merge queue.

You must have a Graphite account in order to use the merge queue. Sign up using this link.

An organization admin has enabled the Graphite Merge Queue in this repository.

Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.

This stack of pull requests is managed by Graphite. Learn more about stacking.

[rmrt1n]

LGTM. Don't merge yet to make review of the upstack PR easier. We'll merge the whole stack at once once everything is reviewed.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
130	1	129	0

View the full list of 1 ❄️ flaky test(s)

::TestMain

Flake rate in main: 100.00% (Passed 0 times, Failed 1 times)

Stack Traces | 0s run time

FAIL	github..../world-engine/pkg/cardinal [build failed]

To view more test analytics, go to the Test Analytics Dashboard
_{📋 Got 3 mins? Take this short survey to help us improve Test Analytics.}