fix(diagram): restore auto-layout reading zoom to 85%

Keep DIAGRAM_READABLE_MIN_SCALE at 0.85 so architecture and mind-map auto layout stay at the previous reading size.

packages/shared/src/diagram-flowchart-style.test.mjs

@@ -122,6 +122,6 @@ describe("flowchart readable viewport", () => {
   test("refuses to shrink a tall flow below reading size", () => {
     expect(flowchartFitsReadableViewport({ width: 220, height: 1680 }, viewport)).toBe(false);
     expect(FLOWCHART_READABLE_MIN_SCALE).toBe(DIAGRAM_READABLE_MIN_SCALE);
-    expect(DIAGRAM_READABLE_MIN_SCALE).toBe(0.75);
+    expect(DIAGRAM_READABLE_MIN_SCALE).toBe(0.85);
   });
 });

packages/shared/src/diagram-flowchart-style.ts

@@ -43,7 +43,7 @@ export const FLOWCHART_LAYOUT_SPACING = { rank: 56, node: 36 };
 
 // Auto layout and opening stay at reading size. Shrinking the whole graph into
 // the viewport makes large notes unreadable; show the start and let the canvas scroll.
-export const DIAGRAM_READABLE_MIN_SCALE = 0.75;
+export const DIAGRAM_READABLE_MIN_SCALE = 0.85;
 export const FLOWCHART_READABLE_MIN_SCALE = DIAGRAM_READABLE_MIN_SCALE;
 
 export const flowchartFitsReadableViewport = (