Make the source pass the CI lint

The central pipeline lints where the old inline one did not, and it
aborts on any warning. Nothing here was actually wrong: 166 of the 243
warnings were the TIC-80 API and the game's own globals being undeclared,
which is what .luacheckrc is for — the same shape impostor already uses.

The rest was trailing whitespace on 14 lines, now stripped. INPUT_KEY_X
is unused but kept: it belongs to the LEFT/RIGHT/A/B/X/Y set and removing
it would leave a gap in the mapping, so luacheck is told to allow the
family.

Verified locally by merging the sources the way the pipeline does and
running luacheck over the result: 0 warnings, 0 errors.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

inc/window/window.intro.lua

@@ -1,9 +1,9 @@
-function IntroWindow.draw() 
+function IntroWindow.draw()
   local x = (Config.screen.width - 132) / 2 -- Centered text
   Print.text(Context.intro.text, x, Context.intro.y, Config.colors.green)
 end
 
-function IntroWindow.update() 
+function IntroWindow.update()
   Context.intro.y = Context.intro.y - Context.intro.speed
 
   -- Count lines in intro text to determine when scrolling is done