Skill picker in assistant citation comments ($ and /)

[NicoM701]

When I comment on a cited assistant passage, I want to use a skill on that passage without leaving the comment box. Typing $ or / in a citation comment today gives me no suggestions. The comment editor is a plain textarea on current main, so there is nothing to pick from.

The main composer already lists $ skills, and skill entries under / when "Show skills in slash menu" is on. I can write the skill next to the citation and move on, but that keeps the skill request separate from what I wrote about that passage. With several quoted passages I also lose which skill goes with which comment.

What I am after on web and desktop:

• $ suggests the skills available for the selected environment, provider and workspace, under the same eligibility rules as the composer.
• / suggests skill entries when "Show skills in slash menu" is on. Skills only, so no /model, mode switches or provider commands.
• Picking a suggestion only edits the comment. Save, send and cancel keep their current shortcuts.

The chosen skill should actually be used on that passage. A $name string sitting in the comment text is not the outcome I want. Comments are stored inside citation links, so I would verify the actual provider-bound skill invocation rather than assume inserting $name is enough. I would treat whatever representation the real invocation needs as part of the agreed scope, and I would account for the open citation delivery work in #16327 and #16389 rather than opening a PR that guesses at it.

Is that direction and scope welcome, or is the main composer the better place for skill selection? I am fine either way. If it fits, I can implement it with focused tests and before/after UI evidence.

[OscarSwanros]

The same gap applies to @. In a citation comment there's no thread, file or folder picker, so I can't point a cited passage at another thread (e.g. "What did @Cueva find missing here?") the way I can in the composer.

If this direction is welcome, it seems worth scoping all three composer pickers (@, $, /) for the comment box together, since they share the same cause (AssistantCitationCommentEditor is a plain textarea) and the same delivery question in #16327: a mention has to reach the provider as a real thread/file reference, not as text inside the citation link.