When a study is cancelled mid-way and the user selects 'Run additional
trials', settings.n_trials was incremented by n_additional_trials,
accumulating the original total into the new count. E.g. cancelling 200
trials at 30 and adding 10 gave n_trials=210 instead of 40, causing
'Running trial 31 of 210...' and planning 180 more trials instead of 10.
Fix by recalculating n_trials from actual completed trials + additional,
so the total reflects the new intended target, not the old one.
Fixes#379
Co-authored-by: Claude <noreply@anthropic.com>
