Packet-aware timing solver qualification

The completed timing checks found a sharp change in the local time-alignment derivative across an IMU packet boundary. This candidate rebuilds its local model on each side before accepting a timing correction.

The qualification plan fixes 67 known-answer software checks, including piecewise timing examples and an explicit test that a genuine cusp cannot bypass the original convergence gate. No archival measurements are fitted here.

Candidate: analysis/lll/ilvis0_solver_timing.py. The qualification worker is analysis/tests/ilvis0_timing_qualification_worker.py; it uses four numerical threads, one sealed test batch and a ten-minute timeout. Completed batches cannot restart. Only complete software qualification permits the separately frozen four-start observed comparison described in the plan.