feat(tui): task list search with / (#10908)

### Description

Add task list searching in terminal UI.

<img width="1898" height="1710" alt="CleanShot 2025-10-01 at 04 24
57@2x"
src="https://github.com/user-attachments/assets/d7e2dba2-1d36-4891-86a7-234b4c9edc33"
/>


Features:
- UI hint for searching
- Locks query when the user presses ENTER
- Dims tasks in table list that don't match query

### Testing Instructions

Use the TUI and try:
- Searching by pressing the `/` key
- Cycling tasks with `↑`/`↓` while typing a query
- Pressing ENTER so you can cycle with `j`/`k`

CLOSES TURBO-4197

Author: anthonyshew