fix(stage-tamagotchi): harden overlay isolation and iframe coordinates (#1751)

---------

Co-authored-by-agent: Antigravity <antigravity@gemini.com>

services/computer-use-mcp/src/chrome-semantic-adapter.test.ts

@@ -332,6 +332,36 @@ describe('chromeElementsToTargetCandidates', () => {
     expect(candidates[0].bounds.y).toBe(50 + 88 + 140 + 24)
   })
 
+  it('uses cumulative nested iframe offsets before converting to screen coordinates', () => {
+    const parentFrameOffset = { x: 320, y: 180 }
+    const childFrameOffset = { x: 24, y: 48 }
+    const nestedFrameOffset = {
+      x: parentFrameOffset.x + childFrameOffset.x,
+      y: parentFrameOffset.y + childFrameOffset.y,
+    }
+    const taggedEl = {
+      tag: 'button',
+      text: 'Nested iframe CTA',
+      rect: { x: 12, y: 24, w: 90, h: 32 },
+      _frameId: 9,
+      _frameOffsetX: nestedFrameOffset.x,
+      _frameOffsetY: nestedFrameOffset.y,
+    } as any
+
+    const candidates = chromeElementsToTargetCandidates(
+      [taggedEl],
+      windowBounds,
+      88,
+      0,
+    )
+
+    expect(candidates[0].frameId).toBe(9)
+    expect(candidates[0].bounds.x).toBe(100 + 320 + 24 + 12)
+    expect(candidates[0].bounds.y).toBe(50 + 88 + 180 + 48 + 24)
+    expect(candidates[0].bounds.width).toBe(90)
+    expect(candidates[0].bounds.height).toBe(32)
+  })
+
   it('falls back to function-level frameId when _frameId is absent', () => {
     const el = {
       tag: 'button',

services/computer-use-mcp/src/server/register-desktop-grounding.test.ts

@@ -470,12 +470,14 @@ describe('desktop_click_target handler integration', () => {
 
   it('falls back to OS click when the connected extension transport is read-only', async () => {
     const sm = new RunStateManager()
+    const iframeAbsoluteBounds = { x: 456, y: 390, width: 90, height: 32 }
     const candidate = makeCandidate({
       id: 't_0',
       source: 'chrome_dom',
       selector: '#login-btn',
-      frameId: 0,
+      frameId: 7,
       isPageContent: true,
+      bounds: iframeAbsoluteBounds,
     })
     sm.updateGroundingSnapshot(freshSnapshot([candidate]))
 
@@ -494,7 +496,13 @@ describe('desktop_click_target handler integration', () => {
     expect(result.executionRoute).toBe('os_input')
     expect(result.routeReason).toContain('does not support getClickTarget + clickAt')
     expect(bridge.clickSelector).not.toHaveBeenCalled()
-    expect(executor.click).toHaveBeenCalledOnce()
+    expect(executor.click).toHaveBeenCalledWith({
+      x: 501,
+      y: 406,
+      button: 'left',
+      clickCount: 1,
+    })
+    expect(result.text).toContain('Point: (501, 406)')
   })
 
   // -----------------------------------------------------------------------