Merging `a|b` and `a|c` into `a` moved the listings one at a time: the
`a|b|c` listing landed on `a|c` before that one left for `a`, merged
into it, and its attributes were lost. Every moving listing now leaves
first, then each lands. Each keyword also moves by the closest keyword
merged (`a|b` before `a`), so the order they are given in doesn't
change the result; the keyword filter follows the same way.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Nathaniel LedfordandClaude Opus 5.5
f0689d3271