refactor: sharpen opaque local variable names across org-drill.el

I renamed several cryptic locals to say what they hold: idx to index-var in the pop-random gensym, val to raw-value in the five DRILL_* property getters, q to quality in hypothetical-next-review-dates, m to marker in free-markers, the a/b sort and filter lambdas in order-overdue-entries to entry/other, and dat to card-def in the empty-card-type check.

These are pure renames with no behavior change. Byte-compile and the full unit suite stay green.

0 files changed, 0 insertions, 0 deletions