Corpses with clients in them can no longer perform mech actions (#88959)

## About The Pull Request

Turns out most mech actions only cared about the person attempting to
use them being inside the mech, without checking for things such as the
mob being alive. This fixes that, but required a slight refactoring to
the `ui_status` proc of mechs to account for the three fundamentally
different types of mobs that can pilot a mech.

## Why It's Good For The Game

Fixes #88933

## Changelog

🆑
fix: Corpses at the pilot seat of mechs can no longer toggle the lights,
safeties, cabin sealing, strafing, overclocking, or durand shields, nor
can they rename the mech or configure its equipment.
/🆑

code/modules/tgui/status_composers.dm

@@ -50,7 +50,9 @@
 
 /// Returns a UI status such that those without blocked hands will be able to interact,
 /// but everyone else can only watch.
-/proc/ui_status_user_has_free_hands(mob/user, atom/source)
+/proc/ui_status_user_has_free_hands(mob/user, atom/source, allowed_source)
+	if(allowed_source)
+		return HAS_TRAIT_NOT_FROM(user, TRAIT_HANDS_BLOCKED, allowed_source) ? UI_UPDATE : UI_INTERACTIVE
 	return HAS_TRAIT(user, TRAIT_HANDS_BLOCKED) ? UI_UPDATE : UI_INTERACTIVE
 
 /// Returns a UI status such that advanced tool users will be able to interact,
@@ -110,3 +112,11 @@
 		return UI_CLOSE
 
 	return UI_INTERACTIVE
+
+/// Return UI_INTERACTIVE if the user is inside the target atom, whether they can see it or not.
+/// Return UI_CLOSE otherwise.
+/proc/ui_status_user_inside(mob/user, atom/target)
+	if(target.contains(user))
+		return UI_INTERACTIVE
+
+	return UI_CLOSE