test: stabilize 0.12.0 candidate validation

Full-suite resource contention could make asynchronous renderer assertions and short runtime timing tests fail even though focused runs passed. Limit Vitest to two workers and give the affected UI operations the existing three-second async window.

Also include the approved Linux ARM OpenCode startup note in both feature matrices and release-note languages, and record the successful isolated Linux x64 Host validation of the current-source Runtime activation path.

src/renderer/src/App.test.tsx

@@ -1892,7 +1892,11 @@ describe('App', () => {
         name: /本地工作区/u
       })
     )
-    await screen.findByRole('heading', { name: '设置中心' })
+    await screen.findByRole(
+      'heading',
+      { name: '设置中心' },
+      { timeout: 3000 }
+    )
     fireEvent.click(
       screen.getByRole('tab', { name: '外观' })
     )
@@ -2180,7 +2184,11 @@ describe('App', () => {
           name: /本地工作区/u
         })
       )
-      await screen.findByRole('heading', { name: '设置中心' })
+      await screen.findByRole(
+        'heading',
+        { name: '设置中心' },
+        { timeout: 3000 }
+      )
       fireEvent.click(
         screen.getByRole('tab', { name: '外观' })
       )
@@ -5749,7 +5757,11 @@ describe('App', () => {
     render(<App />)
 
     fireEvent.click(await screen.findByText('本地工作区'))
-    await screen.findByRole('heading', { name: '设置中心' })
+    await screen.findByRole(
+      'heading',
+      { name: '设置中心' },
+      { timeout: 3000 }
+    )
     fireEvent.click(screen.getByRole('tab', { name: '外观' }))
     fireEvent.click(screen.getByRole('radio', { name: /暗色/u }))
 
@@ -9866,7 +9878,10 @@ describe('App', () => {
       target: { value: '打开示例网页' }
     })
     fireEvent.click(await screen.findByLabelText('发送'))
-    await waitFor(() => expect(run).toHaveBeenCalledOnce())
+    await waitFor(
+      () => expect(run).toHaveBeenCalledOnce(),
+      { timeout: 3000 }
+    )
     const conversationId = run.mock.calls[0]?.[0].conversationId
     expect(conversationId).toBeTruthy()