fix: keep the editor typable after clicking a highlighted lint

[mvanhorn]

Issues

Fixes #3721

Description

Root cause: in SuggestionBox.ts the FocusHook attached to the first suggestion button calls node.focus() on every popup open, moving keyboard focus off the editor and onto a <button> (which cannot accept typed text). Escape works because CloseOnEscapeHook closes the popup and restores the saved cursor. The fix is to only auto-focus a suggestion when the popup was opened via the keyboard activation key (double-tap shift/control -> openClosestToCaret), and NOT when it was opened by a pointer click (onPointerDown). PopupHandler will track which path opened the popup and thread an autofocusSuggestion flag through render() -> SuggestionBox() -> suggestions(), so the FocusHook is only wired for keyboard-opened popups. Because the highlight render box uses pointer-events: none, a click lands in the underlying editor element (the pointerdown listener source), so leaving focus there keeps the caret positioned where the user clicked and Delete/typing work immediately, while keyboard-opened popups retain focus for arrow/enter navigation and Escape still restores the cursor.

Demo

N/A - behavioral fix; validated by the tests below.

How Has This Been Tested?

• Happy path: type a misspelled word into a textarea, wait for the red highlight, click the highlight to open the popup, press Delete (or type a character), and assert the textarea value changed and the editor retained focus (document.activeElement is the textarea).
• Popup still usable by mouse: clicking a suggestion button in the click-opened popup still applies the replacement and closes the popup.
• Keyboard-opened popup unchanged: opening via the activation key still focuses the first suggestion so arrow/enter navigation works, and Escape still closes and restores the caret.
• Edge case: clicking a highlight then clicking elsewhere (outside any box) dismisses the popup without leaving focus trapped.

AI Disclosure

• I am a human and didn't use any AI.
• I used LLM features of my editor, but not an agent.
• I used an AI agent interactively.
• I am an agent or I got an agent to do the work autonomously.

Checklist

• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have considered splitting this into smaller pull requests.