computer-use MCP: hit-test returns Dock for all coordinates, blocking all mouse clicks

Bug Description

The left_click tool in the computer-use MCP rejects all click coordinates with the error:

Click at these coordinates would land on '程序坞' (Dock), which is not in the allowed applications

This happens regardless of which application window is visible and focused at the target coordinates. The hit-test consistently resolves every coordinate to the macOS Dock process (com.apple.dock / "程序坞"), even when the coordinates clearly fall within a granted application's window. Since Dock is a system process and cannot be added via request_access (returns not_installed), this creates a deadlock where no mouse clicks can succeed — only keyboard operations work.

Steps to Reproduce

1. Enable the computer-use MCP
2. request_access to grant an application (e.g., Discord at "full" tier)
3. open_application to launch and focus that application
4. Take a screenshot to confirm the app window is visible and covers the target area
5. Call left_click at coordinates clearly inside the app window
6. Result: Error — "Click at these coordinates would land on '程序坞' (Dock), which is not in the allowed applications"
7. Attempting request_access for "程序坞" or "com.apple.dock" returns not_installed

Expected Behavior

The hit-test should identify the topmost visible window at the given coordinates and match it against the granted applications list. Clicks within a granted application's window should succeed.

Actual Behavior

The hit-test always returns the Dock process ("程序坞" / com.apple.dock) for every coordinate, regardless of which windows are actually at those coordinates. This blocks all mouse interactions.

Environment

• OS: macOS 15.x (Darwin 25.5.0)
• Claude Code: Latest version
• Stage Manager: Tested both enabled and disabled — same behavior
• Granted apps: Discord (full tier), Telegram (full tier), Finder (full tier)
• Keyboard tools: key, type, and other keyboard operations work correctly — only mouse clicks are affected

Root Cause Hypothesis

The accessibility-based hit-test that determines which application owns a given screen coordinate appears to be resolving to the Dock process (which manages the desktop/wallpaper layer) instead of the frontmost application window. This may be related to how macOS reports the accessibility hierarchy — the Dock process owns the desktop background layer, and the hit-test may be hitting that layer instead of the window layer above it.

Workaround

Keyboard-only operation (Cmd+K for search, arrow keys for navigation, Return for confirmation, type for text input) can accomplish most tasks, but mouse interaction remains completely unusable.