feat: add scroll container prop

[DaffPunks]

If editor placed in scrollable container, this happens:

2026-06-30.21.53.49.mov

Because isStickyActive depends on window.addEventListener('scroll', ...). When window is not scrollable, toolbar don't add class: g-md-editor-sticky_sticky-active

Now, with scrollContainerRef if behaves like this:
https://preview.gravity-ui.com/md-editor/1166/?path=/story/experiments-sticky-toolbar-in-scroll-container--story

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Summary by Sourcery

Add support for sticky toolbars that work inside a custom scroll container instead of only the browser window.

New Features:

• Introduce an optional scrollContainerRef prop across editor and toolbar views to enable sticky behavior within a specified scrollable container.
• Add a demo Storybook story showcasing a markdown editor with a sticky toolbar inside a scrollable container.

Enhancements:

• Extend the useSticky hook to listen to scroll-related events on a provided container element and compute stickiness relative to that container.
• Adjust MarkdownEditorView styling to handle layouts when a custom scroll container is used via a dedicated modifier class.

[sourcery-ai]

Reviewer's Guide

Add support for sticky toolbars inside a custom scroll container by extending useSticky to accept a scrollContainerRef, wiring the prop through editor view/toolbar components, and documenting the behavior with a new Storybook experiment.

File-Level Changes

Change	Details	Files
Extend sticky behavior hook to work with either the window or a provided scroll container element.	Introduce CONTAINER_EVENTS set and a getTarget helper to route scroll-related events to either window or the scroll container. Add optional scrollContainerRef parameter to useSticky and compute naturalTopFromContainer based on element and container bounding rectangles. Adjust stickyActive calculation to use scrollContainer.scrollTop when a container is provided, while preserving existing window-based logic as fallback. Update event listener registration and cleanup to use getTarget instead of hard-coded window.	packages/editor/src/react-utils/useSticky.ts
Propagate scrollContainerRef through editor view, toolbar, and settings components so sticky toolbars can track container scrolling.	Add optional scrollContainerRef to ViewProps, ToolbarViewProps, MarkupEditorViewProps, and WysiwygEditorViewProps type definitions. Pass scrollContainerRef from MarkdownEditorView through EditorWrapper, toolbar render paths, Settings, and ToolbarView components. Use scrollContainerRef when calling useSticky in Settings and ToolbarView so sticky state is based on container scroll. Add withScrollContainer modifier class when scrollContainerRef is present and define corresponding SCSS rule to relax height constraints.	packages/editor/src/bundle/MarkdownEditorView.tsx packages/editor/src/bundle/ToolbarView.tsx packages/editor/src/bundle/MarkupEditorView.tsx packages/editor/src/bundle/WysiwygEditorView.tsx packages/editor/src/bundle/MarkdownEditorView.scss
Add a Storybook demo showcasing sticky toolbar behavior inside a scrollable container.	Create EditorWithStickyInContainer component that wraps MarkdownEditorView in a fixed-height scrollable div and passes scrollContainerRef to the editor. Initialize a markdown editor instance with rich initial content to ensure scrolling within the container. Register a new Storybook story under 'Experiments / Sticky Toolbar in Scroll Container' using EditorWithStickyInContainer.	demo/src/stories/experiments/sticky-toolbar/Editor.tsx demo/src/stories/experiments/sticky-toolbar/StickyToolbar.stories.tsx

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[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• The naturalTopFromContainer value is computed only once on mount, so if the layout or container padding changes after initial render the sticky threshold will be off; consider recalculating it inside observe() or when relevant reflow events fire.
• The scrollContainer reference and getTarget are captured once in useEffectOnce, so if scrollContainerRef.current ever changes (e.g. different container or ref reassignment) listeners will still be attached to the old target; if that’s a valid use case, you may want to re-run the effect when the ref changes.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The `naturalTopFromContainer` value is computed only once on mount, so if the layout or container padding changes after initial render the sticky threshold will be off; consider recalculating it inside `observe()` or when relevant reflow events fire.
- The `scrollContainer` reference and `getTarget` are captured once in `useEffectOnce`, so if `scrollContainerRef.current` ever changes (e.g. different container or ref reassignment) listeners will still be attached to the old target; if that’s a valid use case, you may want to re-run the effect when the ref changes.

## Individual Comments

### Comment 1
<location path="packages/editor/src/react-utils/useSticky.ts" line_range="60" />
<code_context>
-            const refPageOffset = elemRef.current.getBoundingClientRect().top;
-            const stickyOffset = parseInt(getComputedStyle(elemRef.current).top, 10);
-            const stickyActive = refPageOffset <= stickyOffset;
+            const stickyOffset = parseInt(getComputedStyle(elemRef.current).top);
+
+            let stickyActive: boolean;
</code_context>
<issue_to_address>
**nitpick:** Explicitly pass a radix to `parseInt` for clarity and robustness

The previous code used `parseInt(..., 10)`; omitting the radix now relies on environment defaults and may conflict with lint rules. Restoring `10` keeps the behavior explicit and consistent across environments.
</issue_to_address>

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[gravity-ui]

[gravity-ui]

[d3m1d0v]

I think it's better to move this to the observe()

[d3m1d0v]

Please, move this story to demo/src/stories/examples