fix: rank multi-pattern matches by directed distance

[lettertwo]

With more than one pattern, closest() picked the candidate with the
smallest absolute distance to the cursor. When the cursor sits on a
pattern's only occurrence, the wrapped searchpos reports that same
match again at distance 0, so it beat every other pattern's real
next/previous match and next/previous never left it.

Directed searches now score each candidate by distance in the direction
of travel, with a match on the wrong side of the cursor costing the
full wrap, so a same-position match always loses to another pattern's
genuine match. The undirected nearest-match case keeps the absolute
measure.

The marked retry loop in match_cursor also ranked against the stale
pre-loop position, since Cursor:move() does not update
cursor.location; it now ranks from the match it just moved to.

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