make dollar-mention always clarify item category (skill, app, plugin)

[sayan-oai]

What

Context + Problem

With the introduction of plugins, we now have one more type of $-mentionable item in the TUI's popup menu on $. Apps, skills, and plugins can all have the same user-facing name, and we attempt to distinguish with a category tag suffix, like [App]. This has a few problems:

• We decide to show tags by the text that will be inserted into the conversation, not the actual user-visible text, so two visibly-identical entries can have no clarifying category tag suffix
• The category tag is a suffix and commonly gets cut off by long descriptions
• The skill category tag is currently only displayed on repo skills as [Repo], which is confusing to most users
• The plugin category tag is currently [<marketplace-name>], which is also confusing to most users

Solution

• Always show a prefix category tag that is [Skill], [App], or [Plugin]. No conditional rendering or copy.

Before:

After:

I also feel this clarifies the results at-a-glance while you scroll:

Screen.Recording.2026-03-09.at.6.14.04.PM.mov

Tests

Added + updated tests (including snapshots), tested locally