Root cause (found during 50k sample generation at seed 6975, surfacing as
'ValueError: Number of samples, -187, must be non-negative' from linspace in
_inject_drift): _random_window's best-effort fallback after 50 failed
non-overlap attempts drew start and end from TWO INDEPENDENT random integers,
so end could be < start. The primary loop was consistent (start, start+length).
Fix: reuse the same start in the fallback so end >= start always holds
(overlap is still allowed in best-effort, just no inversion).
- tests/test_synthesis.py: regression sweeping 300 seeds × 4 type combos,
asserting every segment's end >= start. 146 tests passing.
张宗平
0723b257fd