feat(city): style pack, tileset and lighting

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

crates/city/src/render/lighting.rs

@@ -0,0 +1,51 @@
+//! Light and visibility applied to cells.
+
+use crate::render::{Cell, Rgb, Visibility};
+
+/// Darkens a colour by the tile's light level; never below a quarter so the map stays legible.
+pub fn lit(c: Rgb, light: u8) -> Rgb {
+    c.scale(0.25 + 0.75 * (light as f32) / 255.0)
+}
+
+/// Remembered tiles are dim and static; unseen tiles are black.
+pub fn apply_vis(cell: Cell, vis: Visibility) -> Cell {
+    match vis {
+        Visibility::Visible => cell,
+        Visibility::Remembered => Cell {
+            fg: cell.fg.scale(0.35),
+            bg: cell.bg.scale(0.35),
+            bold: false,
+            dim: true,
+            ..cell
+        },
+        Visibility::Unseen => Cell {
+            ch: ' ',
+            fg: Rgb(0, 0, 0),
+            bg: Rgb(0, 0, 0),
+            bold: false,
+            dim: false,
+        },
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::render::{Cell, Rgb};
+
+    #[test]
+    fn lit_scales_between_quarter_and_full() {
+        assert_eq!(lit(Rgb(200, 100, 40), 255), Rgb(200, 100, 40));
+        assert_eq!(lit(Rgb(200, 100, 40), 0), Rgb(50, 25, 10));
+        let c = Cell {
+            ch: 'x',
+            fg: Rgb(200, 200, 200),
+            bg: Rgb(20, 20, 20),
+            bold: true,
+            dim: false,
+        };
+        let r = apply_vis(c, Visibility::Remembered);
+        assert!(r.fg.0 < 100 && r.dim && !r.bold);
+        assert_eq!(apply_vis(c, Visibility::Visible), c);
+    }
+}