feat(UI): always show book's skill cap even if the PC has passed it

[karxi]

Checklist

Required

• I wrote the PR title in conventional commit format.
• I have committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.

Purpose of change

Currently, books stop showing how far they can teach once they can no longer teach the PC. They're still useful for teaching NPCs, though; after that point, only the Read command will show the skill they can teach to.
This synchronizes that functionality for the sake of convenience.

Describe the solution

I made a few very minor edits to item::book_info().

Describe alternatives you've considered

N/A. This was pretty simple.

Testing

Spawn a book → look at the book → set your skill level higher than the book's cap → look at the book again.

Additional context

[scarf005]

fab 0	fab 10

LGTM, i've modified it a bit to colorize the line to brown if player has higher skill than book provides.

[karxi]

I really dislike adding brown to this block—it clashes with the nearby colors. But as long as it's merged, it's an improvement.

[chaosvolt]

Worth noting that brown is already used in the UI elsewhere, mainly in the list of recipes a book can teach. If I recall it's for stuff you're missing other skills for or some other specific "can't learn this yet" condition.

[karxi]

I am well aware! But that specific block only uses cyan, blue, and yellow. The recipe block uses white, grey, and brown.
Orange could be a suitable compromise? At least it's in line with the yellow of the skill number that way.

[chaosvolt]

Yellow could work too. Orange, funny enough, does not exist in the game's color definitions. XD