fix: keep Platform Features tabs visible

The Platform Features tab strip could shrink to zero height inside the scrollable Settings layout, leaving the Magic Notes tab present in the DOM but invisible and unusable. Prevent the strip from shrinking and add a CSS regression guard.

Release note: 修复设置中心“平台功能”中的“魔法笔记”页签不可见、无法点击的问题。

src/renderer/src/WorkspacePrimitives.test.tsx

@@ -91,6 +91,15 @@ describe('WorkspacePrimitives', () => {
     expect(toggleRowStyles).not.toMatch(/padding-top:/u)
   })
 
+  it('keeps Platform Features tabs visible in scrollable Settings', () => {
+    const platformFeaturesTabs = stylesheet.match(
+      /\.platform-features-tabs\s*\{(?<rules>[^}]*)\}/u
+    )?.groups?.rules
+
+    expect(platformFeaturesTabs).toBeDefined()
+    expect(platformFeaturesTabs).toMatch(/flex:\s*0 0 auto;/u)
+  })
+
   it('uses bundled variable fonts and readable shared type tokens', () => {
     expect(rendererEntry).toContain(
       "@fontsource-variable/noto-sans-sc/wght.css"

src/renderer/src/styles.css

@@ -6245,6 +6245,7 @@ button > svg {
   width: fit-content;
   max-width: 100%;
   overflow-x: auto;
+  flex: 0 0 auto;
 }
 
 .platform-features-tabs + .settings-section,