test: cover SQLitePersister construction, lifecycle, and load variants

[adawang1210]

Summary

Coverage analysis showed several public SQLitePersister paths had no tests: from_values, from_config, copy(), the context-manager protocol, pickling (__getstate__/__setstate__, which the parallelism machinery relies on to ship persisters across processes), and the load() branches for app_id=None (latest across apps) and explicit sequence_id. This adds focused unit tests for each; no behavior changes.

Changes made

• tests/core/test_persistence.py: 7 new tests covering constructor classmethods, context-manager connection closing, copy() connection independence, pickle round-trip reconnection, and the remaining load() query branches (including a missing sequence_id returning None).

How to test

pytest tests/core/test_persistence.py

Notes

The app_id=None test asserts shape rather than which app wins: created_at has second resolution in SQLite, so latest-across-apps ordering is non-deterministic for rapid successive writes (asserting a specific winner would be flaky).

Checklist

• Tests added or updated
• All tests pass locally (pytest tests/ --ignore=tests/integration_tests: 580 passed, 5 skipped)
• Commits signed off (git commit -s)
• Pre-commit hooks pass (black, isort, flake8)
• CONTRIBUTING.md guidelines followed

[github-actions]

This PR has had no activity for 95 days.
Closing to keep the PR list manageable.

Feel free to reopen when you are ready to continue.
If the branch has conflicts, a fresh PR against main might be easier.