scoring: include refusal timestamps in capture duration #116

Imported capture duration currently uses successful measurement timestamps only. A later refusal is omitted and refusal-only sessions have null duration. Parse refusal time and include it in last-activity calculation with regressions. Measurements and decision outcomes are unchanged.

Confirmed at a575437 from PR #4 discussion_r4114179705. Deferred under the approved convergence rule: no source-input loss or false PASS was found.