Fix TextServicesManager scan code forwarding for TSF

[calisto-le]

Fixes #11635

Description

TextServicesManager currently passes 0 as the scan code for almost all keys when forwarding keystrokes to TSF.

This change forwards keyArgs.ScanCode instead, so the scan-code bits in the lParam passed to TextServicesContext.Keystroke are populated correctly.

Existing LeftShift/RightShift special handling remains unchanged.

Customer Impact

Text services, IMEs, or TIPs that rely on scan-code information will receive the correct scan code instead of just 0.

Regression

No. The issue reports this as not being a regression.

Testing

.\build.cmd -pack -plat x64 -test

Tested with a sample TextBox application using locally built WPF assemblies.

Manually verified generated lParam values passed to TextServicesContext.Keystroke, including:

• RightCtrl: scan=0x1D, extended=true
• RightAlt / AltGr: scan=0x38, extended=true
• Normal Enter: scan=0x1C, extended=false
• Numpad Enter: scan=0x1C, extended=true
• Dedicated Delete: scan=0x53, extended=true
• Numpad: scan=0x35, extended=true
• LeftShift: scan=0x2A, extended=false, wParam=VK_SHIFT
• RightShift: scan=0x36, extended=false, wParam=VK_SHIFT

Risk

Low.
The change only forwards the existing scan code value.
If there is any more testing to do please let me know.

Microsoft Reviewers: Open in CodeFlow

[miloush]

I suggest the extended key flag is also set as a part of this fix.

[calisto-le]

Added the extended-key flag handling and verified the generated lParam values manually against the Win32 keyboard message layout.
Verified cases see above in Testing.