test: migrate test & utils (#14569)

#### PR Dependency Tree


* **PR #14569** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Chores**
* Upgraded development test tooling to Vitest v4 and added Playwright
browser test integration; normalized test configurations and CI shard
matrix.

* **Tests**
* Added a large suite of new integration tests covering editor flows
(edgeless, database, embeds, images, latex, code, clipboard,
multi-editor, presentation, undo/redo, etc.).
* Removed numerous end-to-end Playwright test suites across the same
feature areas.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

vitest.config.ts

@@ -46,6 +46,11 @@ export default defineConfig({
     },
   },
   test: {
+    projects: [
+      '.',
+      './packages/frontend/apps/electron',
+      './blocksuite/**/*/vitest.config.ts',
+    ],
     setupFiles: [
       resolve(rootDir, './scripts/setup/polyfill.ts'),
       resolve(rootDir, './scripts/setup/lit.ts'),
@@ -66,8 +71,7 @@ export default defineConfig({
     ],
     testTimeout: 5000,
     coverage: {
-      all: false,
-      provider: 'istanbul', // or 'c8'
+      provider: 'istanbul', // or 'istanbul'
       reporter: ['lcov'],
       reportsDirectory: resolve(rootDir, '.coverage/store'),
     },