fix: restore default colour swatch on slider reset

Call the default colour helper during slider reset so the swatch and hex label jump back to the configured initial colour.

app/logic/reset.py

@@ -12,6 +12,20 @@ class ResetMixin:
         self.val_max.set(self.DEFAULTS["val_max"])
         self.alpha.set(self.DEFAULTS["alpha"])
         self.update_preview()
+        try:
+            default_hex = self._default_colour_hex()  # type: ignore[attr-defined]
+        except Exception:
+            default_hex = None
+        if default_hex and hasattr(self, "_parse_hex_colour") and hasattr(self, "_update_selected_colour"):
+            try:
+                rgb = self._parse_hex_colour(default_hex)  # type: ignore[attr-defined]
+            except Exception:
+                rgb = None
+            if rgb:
+                try:
+                    self._update_selected_colour(*rgb)  # type: ignore[arg-type,attr-defined]
+                except Exception:
+                    pass
         default_text = getattr(self, "status_default_text", None)
         if default_text is None:
             default_text = self._t("status.defaults_restored") if hasattr(self, "_t") else "Defaults restored."