Fix the foreground style for find my mouse

[vanzue]

Summary of the Pull Request

Find my mouse should use full transparent window

PR Checklist

• Closes: Find My Mouse makes windows losing focus #42758
• Communication: I've discussed this with core contributors already. If the work hasn't been agreed, this work might be rejected
• Tests: Added/updated and all pass
• Localization: All end-user-facing strings can be localized
• Dev docs: Added/updated
• New binaries: Added on the required places
  • JSON for signing for new binaries
  • WXS for installer for new binaries and localization folder
  • YML for CI pipeline for new test projects
  • YML for signed pipeline
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

Find.my.mouse.cursor.style.fix.mp4

[Copilot]

Pull Request Overview

This PR modifies the FindMyMouse window configuration to improve mouse input transparency and adjust window behavior. The changes include adding window extended styles for mouse transparency and layered rendering, removing a cursor message handler, and modifying window positioning flags.

Key Changes

• Added WS_EX_TRANSPARENT and WS_EX_LAYERED extended window styles at window creation
• Removed WM_SETCURSOR message handler that set the cursor to arrow
• Removed SWP_NOACTIVATE flag from SetWindowPos call in StartSonar()

[Copilot]

Removing the SWP_NOACTIVATE flag will cause the window to activate when positioned, potentially stealing focus from the foreground application. The Find My Mouse overlay should remain non-intrusive and not activate. The flag should be restored, or replaced with SWP_NOACTIVATE to maintain the previous behavior of not activating the window.

Suggested change

	SetWindowPos(m_hwnd, HWND_TOPMOST, GetSystemMetrics(SM_XVIRTUALSCREEN) + 1, GetSystemMetrics(SM_YVIRTUALSCREEN) + 1, GetSystemMetrics(SM_CXVIRTUALSCREEN) - 2, GetSystemMetrics(SM_CYVIRTUALSCREEN) - 2, 0);
	SetWindowPos(m_hwnd, HWND_TOPMOST, GetSystemMetrics(SM_XVIRTUALSCREEN) + 1, GetSystemMetrics(SM_YVIRTUALSCREEN) + 1, GetSystemMetrics(SM_CXVIRTUALSCREEN) - 2, GetSystemMetrics(SM_CYVIRTUALSCREEN) - 2, SWP_NOACTIVATE);

[Copilot]

The WS_EX_LAYERED flag is not needed for CompositionSpotlight, which uses the Windows Composition API rather than layered window functions like SetLayeredWindowAttributes. This flag is only required by the legacy GdiSonar implementations that are not currently used. While this doesn't cause a functional issue, removing it would improve code clarity and avoid potential confusion about the window's rendering approach.

Suggested change

	DWORD exStyle = WS_EX_TRANSPARENT | WS_EX_LAYERED | WS_EX_TOOLWINDOW | Shim()->GetExtendedStyle();
	DWORD exStyle = WS_EX_TRANSPARENT | WS_EX_TOOLWINDOW | Shim()->GetExtendedStyle();