## Summary
Autocomplete popup synchronization already identifies the active token's
range and query, but accepting a result previously discarded that range
and independently recomputed token boundaries around the cursor. Those
calculations could disagree at ambiguous cursor positions. For example,
in `@first| @second` (with `|` marking the cursor at the intervening
space), the popup targets `@second`, while the old acceptance path
replaces `@first`.
This threads the active range through legacy file search, skill
mentions, and mentions-v2 completion. File, image, and mention insertion
now replace the same token that supplied the popup query, and image
completion reuses the shared file insertion path.
## Stack
This is PR 1 of 3. #31191 builds separator and dismissal behavior on
these explicit replacement ranges, and #30463 then fixes token affinity
between adjacent mentions.
Charlie Marsh
d847857f80