Add loading indicator for type-ahead suggestions

[prasadkarmalkar]

What?

Closes #791

Why?

Adds a "breathing dots" loading indicator, next to the text caret, that shows while a type-ahead suggestion request is in progress in the Type Ahead feature.

How?

• Created a new component TypeAheadLoadingIndicator which renders the three dots breathing indicator in editor iframe using createPortal
• It uses the same caret DOMRect that the ghost-text overlay already uses, following the existing useCaretData/ownerDocument pattern in this codebase.
• Added a isLoading indicator in useTypeAheadSuggestion hook, Which is set true for the duration of a request and cleared on success, error, cancellation, and on the existing request timeout.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5
Used for: Creating a POC, comments and reviewing the code. All the code changes are self-reviewed as well.

Testing Instructions

1. Enable the Type Ahead experiment and open a core/paragraph block.
2. Type text that triggers a suggestion (auto debounce, or Ctrl/Cmd+Space for manual trigger) and confirm the three dots appear near the caret while the request is pending, then disappear once the ghost text/suggestion renders.
3. Trigger a request and quickly continue typing/move the caret away. Confirm the indicator disappears and doesn't get stuck.

Screenshots or screencast

Screen.Recording.2026-09-14.at.7.30.49.PM.mov

Changelog Entry

Added - Loading indicator for type-ahead suggestion requests.

[github-actions]

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Co-authored-by: prasadkarmalkar <prasadkarmalkar@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.72%. Comparing base (12417cb) to head (fe829e3).

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #1029   +/-   ##
==========================================
  Coverage      80.72%   80.72%           
  Complexity      2998     2998           
==========================================
  Files            124      124           
  Lines          11978    11978           
==========================================
  Hits            9669     9669           
  Misses          2309     2309           

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