[Terminal][IME][Korean] Ghost duplicate preview of the in-progress (composing) Korean character appears diagonally below the cursor while typing

Does this issue occur when all extensions are disabled?: Yes/No

- VS Code Version: 1.134.0
- OS Version: Windows 11 24H2 26100.8039

Steps to Reproduce:

1. Open the VS Code Integrated Terminal (`Ctrl+``).
2. Switch input mode to Korean (한/영 key).
3. Type Korean by composing jamo (e.g. type "가나다") and observe the screen **while** the character is still composing (before it is finalized).

## Observed behavior

While a character is still **composing** (not yet finalized), a **second copy of the in-progress character appears offset diagonally below/beside** the real character at the cursor — a "ghost" duplicate preview.

- The final stored/output text is **correct** — this is a **display-only** issue, not duplicate typing.
- The ghost **disappears** once the character is confirmed (finalized).
- Happens **only in the Integrated Terminal** — the **editor is unaffected**.
- Does **not** happen in **Windows Terminal (wt)** under the same conditions.

## Attempted / verified

- [x] Full VS Code restart → recurs
- [x] Reset terminal settings to defaults → recurs
- [x] `code --disable-extensions` → recurs (reproduces with all extensions disabled)
- [x] Windows IME "Compatibility" option ON → briefly reduces, recurs after reload
- [x] Windows Terminal (wt): does not occur (usable workaround)