Stabilize Aggregate Output Ordering

[csfh]

Parent

#180

What to build

Make aggregate Process Output order deterministic and useful for cross-process debugging by sorting by timestamp and applying stable tie-breakers.

Acceptance criteria

• Aggregate Manifest Process Output is sorted by timestamp.\n- [ ] Entries with identical timestamps are ordered by Manifest process order.\n- [ ] Entries from the same process preserve per-buffer row order.\n- [ ] Ordering remains stable across renders.\n- [ ] Tests cover timestamp sorting and tie-breaking with controlled output entries.

Blocked by

#190

[csfh]

Starting implementation.

[csfh]

PR ready: https://github.com/modoterra/stasium/pull/197\n\nVerification passed: bun run lint, bun run typecheck, bun run test, bun run format:check. CI checks passed.