refactor(editor): reorg blocksuite ai code (#10372)

### TL;DR

Relocated AI-related code from `presets` directory to a dedicated `ai` directory for better organization and maintainability.

### What changed?

- Moved AI-related code from `blocksuite/presets/ai` to `blocksuite/ai`
- Relocated AI chat block code from `blocksuite/blocks` to `blocksuite/ai/blocks`
- Updated imports across files to reflect new directory structure
- Renamed `registerBlocksuitePresetsCustomComponents` to `registerAIEffects`
- Fixed path references in GitHub workflow file

### How to test?

1. Build and run the application
2. Verify AI functionality works as expected:
   - Test AI chat blocks
   - Check AI panel functionality
   - Verify AI copilot features
   - Ensure AI-related UI components render correctly

### Why make this change?

This restructuring improves code organization by:
- Giving AI features a dedicated directory that better reflects their importance
- Making the codebase more maintainable by grouping related AI functionality
- Reducing confusion by removing AI code from the more general `presets` directory
- Creating clearer boundaries between AI and non-AI related code

packages/frontend/core/src/modules/dnd/services/index.ts

@@ -5,7 +5,7 @@ import {
   type MonitorGetFeedback,
   type toExternalData,
 } from '@affine/component';
-import { createPageModeSpecs } from '@affine/core/components/blocksuite/block-suite-editor/specs/page';
+import { createPageModeSpecs } from '@affine/core/blocksuite/block-suite-editor/specs/page';
 import type { AffineDNDData } from '@affine/core/types/dnd';
 import { BlockStdScope } from '@blocksuite/affine/block-std';
 import {