fix: resolve math formula display abnormal after editing report

This fix addresses the issue where math formulas become corrupted or
incorrectly displayed after editing the generated report in the editor.

**Root Cause:**
The issue occurred due to incompatibility between markdown processing
in the display component and the Tiptap editor:
1. Display component used \[\] and \(\) LaTeX delimiters
2. Tiptap Mathematics extension expects $ and 70868 delimiters
3. tiptap-markdown didn't have built-in math node serialization
4. Math syntax was lost/corrupted during editor save operations

**Solution Implemented:**
1. Created MathematicsWithMarkdown extension that adds markdown
   serialization support to Tiptap's Mathematics nodes
2. Added math delimiter normalization functions:
   - normalizeMathForEditor(): Converts LaTeX delimiters to $/70868
   - normalizeMathForDisplay(): Standardizes all delimiters to 70868
3. Updated Markdown component to use new normalization
4. Updated ReportEditor to normalize content before loading

**Changes:**
- web/src/components/editor/math-serializer.ts (new)
- web/src/components/editor/extensions.tsx
- web/src/components/editor/index.tsx
- web/src/components/deer-flow/markdown.tsx
- web/src/core/utils/markdown.ts
- web/tests/markdown-math-editor.test.ts (new)
- web/tests/markdown-katex.test.ts

**Testing:**
- Added 15 comprehensive tests for math normalization round-trip
- All tests passing (math editor + existing katex tests)
- Verified TypeScript compilation and linting

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

web/src/core/utils/markdown.ts

@@ -2,6 +2,48 @@ export function autoFixMarkdown(markdown: string): string {
   return autoCloseTrailingLink(markdown);
 }
 
+/**
+ * Normalize math delimiters for editor consumption
+ * Converts display delimiters (\[...\], \\[...\\]) to $$ format
+ * Converts inline delimiters (\(...\), \\(...\\)) to $ format
+ * This ensures consistent format before loading into Tiptap editor
+ */
+export function normalizeMathForEditor(markdown: string): string {
+  let normalized = markdown;
+  
+  // Convert display math - handle double backslash first to avoid conflicts
+  normalized = normalized
+    .replace(/\\\\\[([^\]]*)\\\\\]/g, (_match, content) => `$$${content}$$`)  // \\[...\\] → $$...$$
+    .replace(/\\\[([^\]]*)\\\]/g, (_match, content) => `$$${content}$$`);  // \[...\] → $$...$$
+  
+  // Convert inline math - handle double backslash first to avoid conflicts
+  normalized = normalized
+    .replace(/\\\\\(([^)]*)\\\\\)/g, (_match, content) => `$${content}$`)  // \\(...\\) → $...$
+    .replace(/\\\(([^)]*)\\\)/g, (_match, content) => `$${content}$`);    // \(...\) → $...$
+  
+  return normalized;
+}
+
+/**
+ * Normalize math delimiters for display consumption
+ * Ensures all math delimiters are in $$ format for remarkMath/rehypeKatex
+ * This is used by the Markdown display component
+ */
+export function normalizeMathForDisplay(markdown: string): string {
+  let normalized = markdown;
+  
+  // Convert all LaTeX-style delimiters to $$
+  // Both display and inline math use $$ for display component (remarkMath handles both)
+  // Handle double backslash first to avoid conflicts
+  normalized = normalized
+    .replace(/\\\\\[([^\]]*)\\\\\]/g, (_match, content) => `$$${content}$$`)  // \\[...\\] → $$...$$
+    .replace(/\\\[([^\]]*)\\\]/g, (_match, content) => `$$${content}$$`)      // \[...\] → $$...$$
+    .replace(/\\\\\(([^)]*)\\\\\)/g, (_match, content) => `$$${content}$$`)   // \\(...\\) → $$...$$
+    .replace(/\\\(([^)]*)\\\)/g, (_match, content) => `$$${content}$$`);       // \(...\) → $$...$$
+  
+  return normalized;
+}
+
 function autoCloseTrailingLink(markdown: string): string {
   // Fix unclosed Markdown links or images
   let fixedMarkdown: string = markdown;