Wraps lowertext() to ensure proper stringification. (#82442)

## About The Pull Request

Fixes #82440

This PR just creates a new macro, `LOWER_TEXT()` (yes the irony is not
lost on me) to wrap around all calls of `lowertext()` and ensure that
whatever we input into that proc will be stringified using the `"[]"`
(or `tostring()` for the nerds) operator. very simple.

I also added a linter to enforce this (and prevent all forms of
regression) because I think that machines should do the menial work and
we shouldn't expect maintainers to remember this, let me know if you
disagree. if there is a time when it should be opted out for some
reason, the linter does respect it if you wrap your input with the
`UNLINT()` function.

code/modules/tooltip/tooltip.dm

@@ -112,7 +112,7 @@ Notes:
 		return
 	var/ui_style = user.client?.prefs?.read_preference(/datum/preference/choiced/ui_style)
 	if(!theme && ui_style)
-		theme = lowertext(ui_style)
+		theme = LOWER_TEXT(ui_style)
 	if(!theme)
 		theme = "default"
 	user.client.tooltips.show(tip_src, params, title, content, theme)