fix(editor): recalculate roundness type when switching shape types (#11473)

When converting between generic shapes, the roundness type was only
recalculated when the target type was a diamond. Converting a diamond
(which uses the proportional radius algorithm) back to a rectangle kept
the proportional radius, so rectangles ended up rendering with overly
round corners.

---------

Signed-off-by: Mark Tolmacs <mark@lazycat.hu>
Co-authored-by: Maruthan G <maruthang4@gmail.com>
Co-authored-by: Sivram <withsivram@gmail.com>
Co-authored-by: Jai Kumar Dewani <jai.dewani.99@gmail.com>
Co-authored-by: Mark Tolmacs <mark@lazycat.hu>

packages/excalidraw/tests/helpers/api.ts

@@ -19,8 +19,7 @@ import {
   newTextElement,
 } from "@excalidraw/element";
 
-import { isLinearElementType } from "@excalidraw/element";
-import { getSelectedElements } from "@excalidraw/element";
+import { isUsingAdaptiveRadius, getSelectedElements } from "@excalidraw/element";
 import { selectGroupsForSelectedElements } from "@excalidraw/element";
 
 import { FONT_SIZES } from "@excalidraw/common";
@@ -267,9 +266,9 @@ export class API {
           : rest.roundness
       )
         ? {
-            type: isLinearElementType(type)
-              ? ROUNDNESS.PROPORTIONAL_RADIUS
-              : ROUNDNESS.ADAPTIVE_RADIUS,
+            type: isUsingAdaptiveRadius(type)
+                    ? ROUNDNESS.ADAPTIVE_RADIUS
+                    : ROUNDNESS.PROPORTIONAL_RADIUS,
           }
         : null,
       roughness: rest.roughness ?? appState.currentItemRoughness,