fix: FAITHFUL RATIO works on Android and iOS

apply() returned false on its first line for mobile, so the option did
nothing there. A phone has no window to resize, so the lock caps the
render scale instead: the largest whole multiple of 160x144 the display
holds, centred, black around it.

Two parts beyond that. The scale is read off the display rather than from
the desktop's 1X-4X ladder, which named a different fraction of every
device and left the useful levels off the list; mobile shows ON or OFF.
And the world pass, which expands to cover the whole display so letterbox
becomes more map, is now sized against the locked viewport, so the lock
reaches the overworld instead of showing more of it.

Pixel perfect throughout, whole multiples only. Desktop and OFF are
unchanged. Renames the row to FAITHFUL RATIO on both platforms; the saved
key stays faithfulRes so existing settings carry over.

src/render/Renderer.lua

@@ -12,6 +12,8 @@ local PaletteFX = require("src.render.PaletteFX")
 local Pipelines = require("src.render.Pipelines")
 local PixelCanvas = require("src.render.PixelCanvas")
 local Runtime = require("src.mods.Runtime")
+-- leaf module (no renderer dependency), so requiring it here cannot cycle
+local FaithfulRes = require("src.core.FaithfulRes")
 
 local Renderer = {}
 
@@ -124,7 +126,16 @@ end
 function Renderer:fitScale()
   local _, _, pw, ph = displayMetrics()
   local w, h = self:uiSize()
-  return math.max(1, math.floor(math.min(pw / w, ph / h)))
+  local s = math.max(1, math.floor(math.min(pw / w, ph / h)))
+  -- FAITHFUL RATIO on mobile locks the scale here rather than by resizing the
+  -- window, which a phone does not have (see src/core/FaithfulRes.lua).  The
+  -- cap is the largest WHOLE multiple the display holds, so the picture is as
+  -- big as exact pixels allow and the remainder is bars.  Computed per frame
+  -- off the live drawable size, so a rotate re-derives it with nothing to
+  -- re-apply.
+  local cap = FaithfulRes.scaleCap()
+  if cap and cap < s then s = cap end
+  return s
 end
 
 -- Integer framebuffer pixels per GB pixel for the UI pass.
@@ -224,6 +235,21 @@ end
 -- tilt is inactive).
 function Renderer:worldViewSize()
   local _, _, pw, ph = displayMetrics()
+  -- FAITHFUL RATIO on mobile.  The world pass deliberately expands to cover the
+  -- WHOLE display, so letterbox voids become more map instead of black bars.
+  -- That is why the lock appeared to do nothing in the overworld: it shrank
+  -- the UI blit while the map kept filling the screen -- and showed MORE of
+  -- the map, because a smaller scale fits more world pixels in.
+  --
+  -- Size the view against the LOCKED VIEWPORT rather than the display.  A
+  -- desktop lock gets this for free by making the window exactly 160N x 144N;
+  -- this is the same sum with the viewport standing in for the window, so
+  -- both platforms show the same map area at the same zoom.
+  local cap = FaithfulRes.scaleCap()
+  if cap then
+    local uiw, uih = self:uiSize()
+    pw, ph = uiw * cap, uih * cap
+  end
   local sp = Zoom.scale(self:fitScale())
   local vw, vh = math.ceil(pw / sp), math.ceil(ph / sp)
   -- Even sizes keep Camera:follow on integer pixels (viewW/2 is integral),