FLOWIP-071g: Remove wall-clock tie-breakers from causal ordering

[rocketpages]

Checklist

• I read CONTRIBUTING.md
• All commits are signed off (DCO): git commit -s
• I ran: cargo fmt --all
• I ran: cargo test --workspace

Summary

• Replace timestamp-based tie-breaking with EventId ordering for concurrent events in both disk and memory journals
• Fix a race in DiskJournal where concurrent appends from the same writer could produce duplicate sequence numbers
• Add a shared comparator so both journal implementations use the same ordering logic
• Tighten replay archive version checking to reject archives from a different major.minor framework version
• Add tests for concurrent event ordering, cross-journal parity, and same-writer append safety