### TL;DR
Refactored `SpecProvider` singleton access pattern and reorganized adapter/extension code structure.
### What changed?
- Changed `SpecProvider.getInstance()` to `SpecProvider._` for cleaner singleton access
- Moved adapter/extension code from `_common` directory to dedicated `adapters` and `extensions` folders
- Consolidated adapter extensions into a single file
- Removed unused dependencies from package.json
- Deleted unnecessary schema files
- Extracted `MobileSpecsPatches` class into the mobile patching code
- Updated all references to use the new `SpecProvider._` accessor
### How to test?
- Verify all specs are properly registered and accessible via `SpecProvider._`
- Test adapter functionality for HTML, Markdown, Notion HTML and plain text
- Check mobile-specific features and patches work correctly
- Ensure preview functionality works in both page and edgeless modes
### Why make this change?
- Improves code organization by properly separating adapters and extensions
- Simplifies singleton access pattern
- Removes unnecessary dependencies and files
- Makes the codebase more maintainable by consolidating related functionality
### TL;DR
Moved image proxy middleware and adapter extensions to their respective packages and introduced a new spec provider for adapter registration.
### What changed?
- Relocated `defaultImageProxyMiddleware` from blocks to `@blocksuite/affine-block-image`
- Moved `PresentTool` from fragment-frame-panel to block-frame
- Created new adapter extension specs for HTML, Markdown, and Notion HTML
- Introduced a spec provider pattern for adapter registration
- Removed direct transformer references from RootService
- Updated imports across affected files to use new locations
### How to test?
1. Verify image proxy functionality works in exports and imports
2. Test HTML, Markdown, and Notion HTML adapters still function correctly
3. Confirm presentation mode works with the relocated PresentTool
4. Check that all file import/export operations continue to work as expected
### Why make this change?
This reorganization improves code modularity by placing features in their logical packages and introduces a more maintainable pattern for adapter registration. The spec provider pattern makes it easier to manage and extend adapter functionality while reducing coupling between components.
