feat(editor): improve latex editing support (#14924)

## Summary
- support converting selected text into inline LaTeX equations
- support turning text blocks into LaTeX equation blocks
- add equation entries to editor toolbars while keeping inline equation
with text formatting actions

## Tests
- yarn tsc -b blocksuite/affine/inlines/latex/tsconfig.json
blocksuite/affine/blocks/note/tsconfig.json
blocksuite/affine/blocks/root/tsconfig.json
blocksuite/affine/rich-text/tsconfig.json
blocksuite/affine/widgets/keyboard-toolbar/tsconfig.json --pretty false
- git diff --check origin/canary...HEAD

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

* **New Features**
  * Equation block support with conversion from existing blocks.
  * Inline LaTeX insertion added to the inline formatting toolbar.
* Equation action added to the keyboard toolbar; Equation blocks
searchable via math/equation/latex aliases.

* **Improvements**
* Inline LaTeX editor opens and syncs more reliably; selection/convert
flow preserves distinct LaTeX values when converting in reverse order.

* **Tests**
  * New e2e tests for inline LaTeX conversions and value preservation.

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blocksuite/affine/rich-text/src/conversion.ts

@@ -13,6 +13,7 @@ import {
   QuoteIcon,
   TextIcon,
 } from '@blocksuite/affine-components/icons';
+import { TeXIcon } from '@blocksuite/icons/lit';
 import type { TemplateResult } from 'lit';
 
 /**
@@ -119,6 +120,15 @@ export const textConversionConfigs: TextConversionConfig[] = [
     hotkey: [`Mod-Alt-c`],
     icon: CodeBlockIcon,
   },
+  {
+    flavour: 'affine:latex',
+    type: undefined,
+    name: 'Equation',
+    description: 'Formula block with LaTeX rendering.',
+    hotkey: null,
+    icon: TeXIcon(),
+    searchAlias: ['mathBlock', 'equationBlock', 'latexBlock'],
+  },
   {
     flavour: 'affine:paragraph',
     type: 'quote',