This patch modifies the Taskflow engine to 'parallel' when using
native thread mode and introduces a new test fixtures for
multi-threaded testing:
* DatabaseWriteLock: Serializes database writes by wrapping
_session_for_write with threading.RLock, preventing race conditions
in SQLite-based tests with limited concurrency support.
to the existing TempDir fixture.
Related-Bug: #2133505
Assisted-by: claude-code (Sonnet 4.5)
Change-Id: I3883d3b34691f076bde6ecec109bac94cfa12dd9
Signed-off-by: Douglas Viroel <viroel@gmail.com>
64d101d47d