Microsoft Pinyin IME can't switch to Chinese in WT 1.24 on Win11 25H2 Build 26200

### Windows Terminal version

1.24.11911.0

### Windows build number

Windows 11 25H2, Build 26200.8875

### Other Software

- Shell: PowerShell 7.6.4
- IME: Microsoft Pinyin (new version, TSF3, NOT compatibility mode)

### Steps to reproduce

1. Use Windows 11 25H2 (Build 26200) with the latest Windows updates (KB5100998, KB5101650, KB5120102 installed on 2025-07-25)
2. Ensure Microsoft Pinyin IME is using the new version (NOT enabled "Use previous version of Microsoft Pinyin IME" compatibility mode)
3. Open Windows Terminal (any profile, e.g. PowerShell)
4. Press Shift (or Ctrl+Space) to switch to Chinese input mode

### Expected Behavior

IME switches to Chinese input mode. Candidate/composition UI appears. Can type Chinese characters.

### Actual Behavior

Shift key (and other IME switch shortcuts) have no effect. IME stays in English mode. Can only type English letters.
Chinese input works fine in all non-terminal apps (Notepad, browser, etc.).

### Workaround

Enable "Use previous version of Microsoft Pinyin IME" in Windows Settings → Time & Language → Language & Region → Chinese → Microsoft Pinyin → Keyboard Options → General → Compatibility. This forces the IME back to the older TSF2 stack and Chinese input works again. But the old IME has an outdated UI.

### Additional context

- This started after the Windows 25H2 updates on 2025-07-25. Before those updates, the new Microsoft Pinyin IME worked correctly in WT.
- This appears related to the TSF3 changes in the newer Microsoft Pinyin IME interacting with WT's TSF layer.
- Similar to #19722 and #19670 which were fixed by #19738 (removing TF_TMAE_UIELEMENTENABLEDONLY), but #19738 is already in WT 1.24.11911.0 and does NOT fix this issue.
- Registry analysis shows `NoTsf3Override2 = 0` under `HKCU\Software\Microsoft\Input\TSF\tsf3override\{81d4e9c9-1d3b-41bc-9e6c-4b40bf79e35e}`, confirming the IME is using TSF3.
- Multiple users reporting the same issue (see CSDN article: https://blog.csdn.net/2401_87486264/article/details/163264725, same environment: WT 1.24 + Win11 25H2 + pwsh 7.6)

Reproduce the failure on Windows 11 25H2 with Microsoft Pinyin in new TSF3 mode, following the listed steps, then compare the current behavior with related issues #19722, #19670, and fix #19738. Investigate Windows Terminal's TSF handling and verify that switching to Chinese and showing the candidate/composition UI works without requiring compatibility mode.

Written by the indexing model from the issue text.