refactor: reorganize specs and adapter extensions (#10359)

### 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

blocksuite/affine/block-embed/src/common/render-linked-doc.ts

@@ -197,7 +197,7 @@ async function renderNoteContent(
     match: ids.map(id => ({ id, viewType: 'display' })),
   };
   const previewDoc = doc.doc.getStore({ query });
-  const previewSpec = SpecProvider.getInstance().getSpec('preview:page');
+  const previewSpec = SpecProvider._.getSpec('preview:page');
   const previewStd = new BlockStdScope({
     store: previewDoc,
     extensions: previewSpec.value,

blocksuite/affine/block-embed/src/embed-synced-doc-block/embed-synced-doc-block.ts

@@ -118,7 +118,7 @@ export class EmbedSyncedDocBlockComponent extends EmbedBlockComponent<EmbedSynce
 
   protected _buildPreviewSpec = (name: 'preview:page' | 'preview:edgeless') => {
     const nextDepth = this.depth + 1;
-    const previewSpecBuilder = SpecProvider.getInstance().getSpec(name);
+    const previewSpecBuilder = SpecProvider._.getSpec(name);
     const currentDisposables = this.disposables;
     const editorSetting =
       this.std.getOptional(EditorSettingProvider) ??

blocksuite/affine/block-root/src/edgeless/components/frame/frame-preview.ts

@@ -80,8 +80,7 @@ export class FramePreview extends WithDisposable(ShadowlessElement) {
 
   private _previewDoc: Store | null = null;
 
-  private readonly _previewSpec =
-    SpecProvider.getInstance().getSpec('preview:edgeless');
+  private readonly _previewSpec = SpecProvider._.getSpec('preview:edgeless');
 
   private readonly _updateFrameViewportWH = () => {
     const [, , w, h] = deserializeXYWH(this.frame.xywh);

blocksuite/affine/block-root/src/transformers/html.ts

@@ -26,7 +26,7 @@ type ImportHTMLZipOptions = {
 
 function getProvider() {
   const container = new Container();
-  const exts = SpecProvider.getInstance().getSpec('store').value;
+  const exts = SpecProvider._.getSpec('store').value;
   exts.forEach(ext => {
     ext.setup(container);
   });

blocksuite/affine/block-root/src/transformers/markdown.ts

@@ -16,7 +16,7 @@ import { createAssetsArchive, download, Unzip } from './utils.js';
 
 function getProvider() {
   const container = new Container();
-  const exts = SpecProvider.getInstance().getSpec('store').value;
+  const exts = SpecProvider._.getSpec('store').value;
   exts.forEach(ext => {
     ext.setup(container);
   });

blocksuite/affine/block-root/src/transformers/notion-html.ts

@@ -14,7 +14,7 @@ type ImportNotionZipOptions = {
 
 function getProvider() {
   const container = new Container();
-  const exts = SpecProvider.getInstance().getSpec('store').value;
+  const exts = SpecProvider._.getSpec('store').value;
   exts.forEach(ext => {
     ext.setup(container);
   });

blocksuite/affine/block-surface-ref/src/portal/note.ts

@@ -118,7 +118,7 @@ export class SurfaceRefNotePortal extends WithDisposable(ShadowlessElement) {
       query: this.query,
       readonly: true,
     });
-    const previewSpec = SpecProvider.getInstance().getSpec('preview:page');
+    const previewSpec = SpecProvider._.getSpec('preview:page');
     return new BlockStdScope({
       store: doc,
       extensions: previewSpec.value.slice(),

blocksuite/affine/block-surface-ref/src/surface-ref-block.ts

@@ -239,8 +239,7 @@ export class SurfaceRefBlockComponent extends BlockComponent<SurfaceRefBlockMode
 
   private _previewDoc: Store | null = null;
 
-  private readonly _previewSpec =
-    SpecProvider.getInstance().getSpec('preview:edgeless');
+  private readonly _previewSpec = SpecProvider._.getSpec('preview:edgeless');
 
   private _referencedModel: GfxModel | null = null;
 

blocksuite/affine/shared/src/utils/spec/spec-provider.ts

@@ -17,7 +17,7 @@ export class SpecProvider {
 
   private constructor() {}
 
-  static getInstance() {
+  static get _() {
     if (!SpecProvider.instance) {
       SpecProvider.instance = new SpecProvider();
     }

blocksuite/affine/widget-drag-handle/src/helpers/preview-helper.ts

@@ -102,7 +102,7 @@ export class PreviewHelper {
     const editorSetting = std.get(EditorSettingProvider).peek();
     const query = this._calculateQuery(blockIds as string[], mode);
     const store = widget.doc.doc.getStore({ query });
-    const previewSpec = SpecProvider.getInstance().getSpec(
+    const previewSpec = SpecProvider._.getSpec(
       isEdgeless ? 'preview:edgeless' : 'preview:page'
     );
     const settingSignal = signal({ ...editorSetting });