This PR make out-of-viewport but selected edgeless block keep active, since the selected block may still have some user interactions on the DOM. For example, when hover on a selected note and scroll viewport by wheel to view its hidden content, the note should not be hidden (a.k.a idel).
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **Refactor**
- Updated viewport logic to keep selected items visible instead of only those being edited. Visibility now depends on selection status rather than editing state.
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Close [BS-3066](https://linear.app/affine-design/issue/BS-3066/优化长note的展示和折叠)
- Enhanced the visibility behavior of hidden content in edgeless notes by:
- Showing hidden content when a note is being edited, even when it's outside the viewport
- Improving hover behavior with a delay when leaving from the bottom of the note
- Adding proper cleanup of hover timeouts when the component is disconnected
- Optimizing the viewport element to keep editing blocks or elements visible
## Testing
- Added new E2E test cases covering:
- Hover behavior on selected notes
- Content visibility during editing
- Viewport scrolling behavior
- Edge cases for content visibility
## Impact
This change improves the user experience when working with collapsed notes in edgeless mode by making the content more accessible and preventing accidental content hiding during editing.
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
- **Bug Fixes**
- Improved visibility of hidden content in edgeless notes when hovering near the bottom edge or editing the note, especially after resizing or clipping.
- **New Features**
- Enhanced hover behavior with delayed clearing based on mouse position to improve user experience.
- **Tests**
- Added new tests verifying hidden content visibility in edgeless notes during hover and editing, simulating diverse user interactions.
- **Chores**
- Added utilities to get and set viewport center for improved test control.
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Close [BS-2866](https://linear.app/affine-design/issue/BS-2866/presentation-mode中的note消失)
## Problem
When using RequestAnimationFrame (RAF) for GFX block updates, there was a timing issue where the transform update would lag behind the RAF callback, causing the block to display with the previous frame's transform state.
## Solution
1. Refactored the block state management to use signals for better reactivity
2. Moved block visibility state management from `viewport-element.ts` to `gfx-block-component.ts`
3. Added `transformState$` signal to track block state
4. Synchronized transform updates with RAF using `effect` to ensure updates happen in the correct frame
5. Added test case to verify note visibility in presentation mode
