UI in device pixels on the character grid with fixed integer font sizes, ASCII bars; 3D render scale for a pixel look

- text only at 1x/2x/4x times an integer interface factor (auto or 1-4 in the settings)
- high DPI rendering, own 2D camera in device pixels, mouse converted
- toolbar buttons 6 columns, integer icon scale, minimap integer pixels per tile
- all bars (top bar, unit/tower/gate HP) as CP437 block characters
- 3D world optionally rendered at 1/2, 1/3, 1/4 and upscaled with nearest filtering

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/settings.rs

@@ -141,7 +141,8 @@ pub struct Settings {
     pub outlines: bool,
     pub wall_detail: u8, // 1 low, 2 medium, 3 high
     pub max_lights: u8,  // 8, 16 or 24
-    pub ui_scale: u8,    // font scale 2 (normal) or 3 (large)
+    pub ui_factor: u8,   // interface size: 0 = automatic, 1..4 = fixed integer factor
+    pub render_scale: u8, // 3D world resolution divisor: 1 = full, 2..4 = pixel look
     // game
     pub game_speed: f32, // 1 or 2
     pub hints: bool,
@@ -165,7 +166,8 @@ impl Default for Settings {
             outlines: true,
             wall_detail: 2,
             max_lights: 24,
-            ui_scale: 2,
+            ui_factor: 0,
+            render_scale: 1,
             game_speed: 1.0,
             hints: true,
             map_w: 64,