feat: add AA in headless exports

CLAUDE.md

@@ -41,7 +41,8 @@ Native CLI flags (`src/cli.rs`, applied in `FractalApp::apply_cli`): `--kind`,
 `--power`, `--julia re,im`, `--phoenix-p re,im`, `--lambda-l re,im`,
 `--palette`, `--share <fragment>`,
 `--view re,im,half_height[,iterations]`, `--rendering-kind`,
-`--yaw`/`--pitch` (3D camera, degrees), `--de`, `--buddhabrot`,
+`--yaw`/`--pitch` (3D camera, degrees), `--de`, `--antialias` (2×2),
+`--buddhabrot`,
 `--buddha-palette`. `--headless` (`src/headless.rs`) skips the window
 entirely: it builds the same view from the other flags, creates its own
 offscreen wgpu device, and renders straight to a PNG (`--width`/`--height`,

src/app.rs

@@ -847,6 +847,9 @@ impl FractalApp {
         if cli.de {
             self.de_coloring = true;
         }
+        if cli.antialias {
+            self.antialias = true;
+        }
         if cli.buddhabrot {
             self.mode = FractalMode::Buddhabrot;
         }

src/cli.rs

@@ -74,6 +74,10 @@ pub struct Cli {
     #[arg(long)]
     pub de: bool,
 
+    /// Enable 2×2 antialiasing (supersampling; ~4× slower).
+    #[arg(long)]
+    pub antialias: bool,
+
     /// Coloring palette index.
     #[arg(long, value_name = "INDEX")]
     pub palette: Option<u32>,