Add Persona picker in Room Input

[j0lol]

Description

Add a PMP/Persona picker in the room input, so a user can switch between personas graphically (without shorthands or /usepmp.)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

[j0lol]

Names and such are in a bit of a rough state but it is MVP "working". Going to work on it a bit more before I'm comfortable un-drafting this.

Screencast_20260721_011126.webm

(In the video the first switch is buggy, but the rest work fine.)

Making UI for plural systems is new territory, so I'd like feedback from other systems if possible. I'm asking around for feedback.

[cyrneko]

fwiw, while I'm here I'll leave some thoughts that j0 already knows of but I didn't share publicly yet:

I believe that good keyboard navigation would be very nice to have, in addition to using prefixes or pk; commands like what Sable already does

I was thinking something like alt+P or alt+↑ might work? From that point on the search is focused, or entries could be manually tabbed/↓↑ through