fix: clear stale end-pos on resume so final-report fires (upstream #33)

When a user interrupted a drill session to edit or capture, the
session's end-pos slot got set to a marker (or :quit).  The end-of-
org-drill cond branched on end-pos: if set, show resume message and
skip org-drill-final-report.

That worked for the first interruption.  But on org-drill-resume,
the session was reused with end-pos still carrying the prior marker.
Even when the resumed session completed normally, the same cond
branch fired again — silently skipping final-report.

Clear end-pos at the top of org-drill when resume-p is non-nil, per
Markus's proposed patch on the upstream issue.  The resumed session
can now reach the final-report branch.

0 files changed, 0 insertions, 0 deletions