Select tab panel when caret moves into tab

[jeryj]

What?

Updates the Tabs block so that moving the caret into a tab's label in the editor activates that tab's panel, matching the existing click behavior.

Why?

In the editor, the active tab panel only switched when you clicked a tab. Moving the caret into a different tab label with the keyboard left the previously selected panel showing — you had to click in the editor to update which panel was visible. This is inconsistent and breaks keyboard-only editing of tabs.

How?

All tab labels live as RichText fields inside a single core/tab-list block, so moving the caret between labels with the keyboard never changes the selected block and never fired the existing click/selection handlers that update the active panel.

In tab-list/edit.js:

• Renamed handleTabClick to selectTabPanel, since it sets the active panel regardless of how it's triggered.
• Replaced the onClick handler with an onFocus handler on each tab button that calls selectTabPanel( index ). React's onFocus bubbles (via focusin) from the inner RichText editable, so focus landing in a tab label activates the matching panel.

selectTabPanel already no-ops when the target tab is already active and marks the change as non-persistent (kept out of undo history), so the added onFocus is safe alongside the click path.

Testing Instructions

1. Add a Tabs block to a post with at least two tabs, each with distinct panel content.
2. Click into the first tab's label — confirm the first panel is shown.
3. Without clicking the editor canvas, move the caret into the second tab's label (see keyboard steps below).
4. Confirm the second tab's panel becomes the visible/active panel as soon as the caret enters its label.

Testing Instructions for Keyboard

1. Add a Tabs block with two or more tabs.
2. Place the caret in the first tab's label and edit its text.
3. Use the arrow keys to move the caret from the first tab label into the next tab label.
4. Confirm the panel updates to the newly focused tab without needing a mouse click.

Screenshots or screencast

Before	After

Use of AI Tools

I used Claude Code to investigate the cause and draft the change.

[github-actions]

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Co-authored-by: jeryj <jeryj@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

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[github-actions]

Size Change: -7 B (0%)

Total Size: 7.49 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-library/index.min.js	324 kB	-7 B (0%)

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[Mamaduka]

Thanks, @jeryj!