config: add window-step-resize option

macos/Sources/Features/Primary Window/PrimaryView.swift

@@ -82,6 +82,7 @@ struct PrimaryView: View {
                         self.window.title = newValue
                     }
                     .onChange(of: cellSize) { newValue in
+                        if !ghostty.windowStepResize { return }
                         guard let size = newValue else { return }
                         self.window.contentResizeIncrements = size
                     }

macos/Sources/Ghostty/AppState.swift

@@ -97,6 +97,15 @@ extension Ghostty {
             return String(cString: ptr)
         }
         
+        /// Whether to resize windows in discrete steps or use "fluid" resizing
+        var windowStepResize: Bool {
+            guard let config = self.config else { return true }
+            var v = false
+            let key = "window-step-resize"
+            _ = ghostty_config_get(config, &v, key, UInt(key.count))
+            return v
+        }
+
         /// The background opacity.
         var backgroundOpacity: Double {
             guard let config = self.config else { return 1 }