Add the captureControls block support and opt in the quote block

[ellatrix]

What?

See #61209. Adds a captureControls block support: while an inner block is selected, the toolbar and inspector keep showing the opted-in ancestor's controls, and the selection shrinks to a tile at the end of the toolbar. Activating the tile expands the selection's own controls. The quote block opts in.

Why?

Selecting a paragraph inside a quote hides the quote's controls, notably the citation toggle. This keeps them in view without changing the selection or locking anything.

How?

1. getControlsCapturingParent (private selector): topmost captureControls ancestor of the selection; content-locked sections take precedence.
2. mayDisplayControls mounts the capturing block's fills and suppresses the selection's.
3. Toolbar, popover anchor, and inspector render the capturing block; a CapturedBlockSelector tile shows the deepest selected block, or the count for a multi-selection.
4. expandedControlsBlock (ephemeral state) disables the capture after the tile is clicked, until the selection leaves the block or lands on it.

Testing Instructions

1. Insert a quote with two paragraphs and click into one: quote toolbar and inspector show, with a paragraph tile at the toolbar's end.
2. Click the tile: paragraph toolbar and inspector show; the sibling paragraph keeps them; selecting the quote or leaving it collapses back.
3. Multi-select both paragraphs: quote toolbar with a "2 blocks" tile.
4. npm run test:e2e -- --project=chromium editor/various/captured-block-controls.spec.js

Testing Instructions for Keyboard

Alt+F10, arrow to the last toolbar item, Enter to expand. Known gap: focus is not moved into the re-rendered toolbar after expanding.

Screenshots or screencast

Collapsed (paragraph selected)	Expanded (after activating the tile)

Use of AI Tools

Authored by Claude (Fable 5) in collaboration with @ellatrix.

[github-actions]

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[github-actions]

Size Change: +1.03 kB (+0.01%)

Total Size: 7.71 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-editor/index.min.js	459 kB	+619 B (+0.14%)
build/scripts/block-library/index.min.js	357 kB	+12 B (0%)
build/styles/block-editor/style-rtl.css	20.2 kB	+105 B (+0.52%)
build/styles/block-editor/style-rtl.min.css	17.2 kB	+101 B (+0.59%)
build/styles/block-editor/style.css	20.2 kB	+97 B (+0.48%)
build/styles/block-editor/style.min.css	17.2 kB	+100 B (+0.58%)

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[Mamaduka]

There's already a __experimentalExposeControlsToChildren Block API; how is this different from it?

Do we have other use cases for this new API? Lots of internal changes and a new concept just for a single block.