Fix undo shortcuts in text fields

[scruffian]

What?

Closes #80541.

See #18755 and #38731.

This PR prevents editor-level undo/redo shortcuts from running when focus is inside an input or textarea.

Why?

Native form controls should keep their browser undo/redo behavior instead of triggering post editor history, which fixes the redesigned Custom HTML modal and related input/textarea cases.

How?

The editor undo/redo shortcut callbacks now return without calling editor history or preventDefault() when the keyboard event target is an input or textarea.

Testing Instructions

1. Open a post or page.
2. Insert a Custom HTML block.
3. Open the HTML editor and type into the HTML, CSS, or JavaScript field.
4. Press Cmd+Z or Ctrl+Z and confirm the focused text field undoes its own text change instead of undoing a block editor change.
5. Confirm Cmd+Z or Ctrl+Z still undoes editor history when focus is not inside an input or textarea.

Testing Instructions for Keyboard

1. Use the keyboard to focus the Custom HTML editor field.
2. Type text, then press Cmd+Z or Ctrl+Z.
3. Confirm the focused text field handles undo, and use Cmd+Shift+Z, Ctrl+Shift+Z, or Ctrl+Y to confirm redo behavior where supported by the browser and OS.

Screenshots or screencast

N/A.

Use of AI Tools

AI tooling used: OpenAI Codex assisted with implementation, tests, and PR preparation; changes were reviewed by the author.

[github-actions]

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Co-authored-by: noruzzamans <noruzzaman@git.wordpress.org>
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[github-actions]

Size Change: +10 B (0%)

Total Size: 7.75 MB

📦 View Changed

Filename	Size	Change
build/scripts/editor/index.min.js	501 kB	+10 B (0%)

_{compressed-size-action}

[github-actions]

Flaky tests detected in bba1cfe.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/29953014845
📝 Reported issues:

• [Flaky Test] should update the HTML only for the latest navigation #78835 in /test/e2e/specs/interactivity/router-navigate.spec.ts

[noruzzamans]

Tested! confirms the fix works as expected. On trunk, pressing Cmd+Z inside the Custom HTML modal undid the block insertion and closed the whole modal. With this fix, Cmd+Z now undoes just the last text change within the field, and the modal stays open.

Screen.Recording.2026-07-22.at.8.15.19.AM.mov

[Mamaduka]

This is not a singular issue - #80541 (comment).

Why are we not updating the attribute directly? Then, the editor history should work normally.

P.S. Utils like stopUndoRedoKeyboardShortcutPropagation probably don't need unit tests.

[Mamaduka]

Can there be a case when a consumer wants to use editor history with normal text fields?

cc @ellatrix, @youknowriad

[youknowriad]

I think this is more complex than it seems. If the input/textarea is part of a block input (maybe the search block for instance), I think you'd want the regular block editor undo/redo no?

[Mamaduka]

Related - #80768.

[scruffian]

Closing in favour of #80768