Extensible site editor: Add a revisions entry point to the Styles route

[youknowriad]

What?

Adds a Revisions entry point to the extensible site editor's Styles route, closing one of the v2 gaps surfaced by the dual-editor e2e run (#82117). The classic site editor and the edit-mode Styles panel both offer a Revisions button; the v2 Styles route had no way to reach style revisions at all.

Why?

The revisions screen itself already ships in the shared @wordpress/global-styles-ui package and is bundled into the GlobalStylesUIWrapper the route renders — deep-linking to ?section=/revisions already worked. What was missing was the entry point and the canvas side of the experience.

How?

• Entry point (routes/styles/stage.tsx): a Revisions button (the usual clock icon) in the route header between the Style Book toggle and the More menu, mirroring the edit-mode Styles panel — disabled (but accessible) while no revisions exist, since the revisions screen has no empty state, and pressed while the revisions screen is open. Clicking toggles the section search param between / and /revisions.
• Canvas preview (routes/styles/stage.tsx): the route's canvas is the editor in preview mode, and EditorInterface already swaps to the revisions preview when the editor store's styles path enters /revisions — edit mode drives that via setStylesPath, the route drives everything via the URL. A small effect syncs the open revisions screen (including the selected revision id) into the store, so selecting a revision previews it in the canvas exactly as in edit mode.
• Style book (routes/styles/canvas.tsx): when the style book preview is toggled on, the canvas is a bare StyleBookPreview that knows nothing about revisions. When a revision is selected, the route now resolves it via useGlobalStylesRevisions (a regular export of @wordpress/global-styles-ui, which routes/font-list already depends on) and passes it as userConfig, matching what edit mode's styles canvas does.
• Preview-mode chrome (packages/editor): StylesCanvas unconditionally rendered its edit-mode chrome — frame padding, a close button, and Escape-to-close. In preview mode the canvas is the whole surface, not a frame opened over an editing session, and the close affordances would only desync whatever opened it (in the route, the rail's back button owns closing). They are now skipped in preview mode and the canvas renders edge to edge. Edit mode is untouched.

Apply already worked through the shared GlobalStylesContext — it edits the global styles entity and the route's save flow picks it up.

Testing Instructions

1. Enable the Extensible site editor experiment and open Styles.
2. With no style revisions, the Revisions button in the Styles panel header is disabled. Make and save a couple of styles changes to create revisions.
3. Click the Revisions button: the revisions list opens in the panel and the canvas shows the revisions preview, edge to edge with no close button.
4. Click through revisions: the canvas previews each selected revision. Click Apply: the screen closes back to the styles root and the save flow shows the pending change.
5. Toggle the Style Book on and select revisions again: the style book previews the selected revision's styles.
6. In the classic site editor / post editor, open Styles → Revisions and confirm the edit-mode canvas still shows the framed preview with its close button (unchanged).

Testing Instructions for Keyboard

On the Styles route, Tab to the Revisions button (it is exposed while disabled), activate it, and traverse the revisions list with arrow keys; the back button in the panel header closes the screen.

🤖 Generated with Claude Code

[github-actions]

Size Change: +85 B (0%)

Total Size: 7.91 MB

📦 View Changed

Filename	Size	Change
build/scripts/editor/index.min.js	580 kB	+37 B (+0.01%)
build/styles/editor/style-rtl.css	31.8 kB	+12 B (+0.04%)
build/styles/editor/style-rtl.min.css	27.2 kB	+11 B (+0.04%)
build/styles/editor/style.css	31.8 kB	+14 B (+0.04%)
build/styles/editor/style.min.css	27.2 kB	+11 B (+0.04%)

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[github-actions]

Flaky tests detected in d1abffb.
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/33090627971
📝 Reported tests:

Should save the changes in /test/e2e/specs/editor/plugins/wp-editor-meta-box.spec.js, passed after 2 failed attempts.

TimeoutError: page.waitForFunction: Timeout 10000ms exceeded.
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/plugins/wp-editor-meta-box.spec.js:34:14
TimeoutError: locator.click: Timeout 10000ms exceeded.
Call log:
  - waiting for locator('role=button[name="Visual"i]')

    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/plugins/wp-editor-meta-box.spec.js:33:55