# Objective

Fix IME candidate window not following cursor position in the integrated
terminal when running fullscreen TUI applications like opencode.

When using IME (Input Method Editor) in Zed's terminal with fullscreen
TUI applications (e.g., opencode), the candidate window does not follow
the cursor position. This issue does not occur in normal terminal usage
(e.g., bash shell).

# Solution

The root cause was three-layer blocking preventing IME position updates
in ALT_SCREEN mode:

1. **ALT_SCREEN blocking**: `selected_text_range()` returned `None` in
ALT_SCREEN mode, causing `selected_bounds()` to return `None`
2. **Missing trigger**: `Event::Wakeup` did not call
`invalidate_character_coordinates()`, so cursor movement did not trigger
IME position updates
3. **Composition blocking**: `update_ime_position()` skipped updates
when `state.composing` was true

Fixes:
- Remove ALT_SCREEN check in `selected_text_range()` so IME position
updates work in fullscreen TUI apps
- Add `window.invalidate_character_coordinates()` in `Event::Wakeup` to
trigger IME position updates when terminal cursor moves
- Remove `state.composing` check in `update_ime_position()` to allow IME
position updates during text-input-v3 composition
- Remove unused `terminal` field from `TerminalInputHandler` struct

# Testing

**Did you test these changes? If so, how?**
- Yes, tested on Linux GNOME Wayland with iBus input method
- Verified IME candidate window correctly follows cursor in opencode
- Verified normal terminal usage with IME still works correctly

**Are there any parts that need more testing?**
- Other IMEs (fcitx, etc.) may need testing

**How can other people (reviewers) test your changes?**
1. Open Zed's integrated terminal
2. Run a fullscreen TUI application like `opencode`
3. Activate IME (e.g., iBus with Chinese input)
4. Type text and observe the IME candidate window follows the cursor

**What platforms did you test these changes on?**
- Linux (GNOME Wayland) - tested
- macOS - not tested (may have different IME behavior)
- Windows - not tested (different code path)

# Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [ ] The content adheres to Zed's UI standards (UX/UI and icon
guidelines)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

# Showcase

<details>
  <summary>Before</summary>
<video
src="https://github.com/user-attachments/assets/ee2fac4e-801b-49af-a57e-32ce25e01db5"
width="320" height="180" />
</details>

<details>
  <summary>After</summary>
<video
src="https://github.com/user-attachments/assets/c669ea99-2ffc-4179-b587-a47873e33e70"
width="320" height="180" />
</details>

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Release Notes:

- Fixed IME candidate window not following cursor in terminal TUI apps