fix: address Copilot review comments for HTML tag support

- Preserve <u> HTML tags for underline instead of converting to _text_
  to avoid conflict with italic styling
- Preserve <sup>/<sub> HTML tags for superscript/subscript instead of
  ^/~ markers to avoid conflicts with regular text
- Use regex pattern for table separator detection to avoid false
  positives when cell content contains "---"
- Escape pipe characters in table cells to prevent markdown table
  structure breakage
- Remove unused headerRowCount variable and related code
- Update tests to reflect new behavior
- Add test for pipe escaping in table cells

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: graycreate

V2er/Sources/RichView/Converters/HTMLToMarkdownConverter.swift

@@ -190,19 +190,19 @@ public class HTMLToMarkdownConverter {
                     let content = try convertElement(childElement)
                     result += "~~\(content)~~"
 
-                // Underline - no standard markdown, render as emphasized text
+                // Underline - no standard markdown, preserve as HTML for custom renderer
                 case "u", "ins":
                     let content = try convertElement(childElement)
-                    result += "_\(content)_"
+                    result += "<u>\(content)</u>"
 
-                // Superscript/subscript - render with markers
+                // Superscript/subscript - preserve as HTML for custom renderer
                 case "sup":
                     let content = try convertElement(childElement)
-                    result += "^\(content)"
+                    result += "<sup>\(content)</sup>"
 
                 case "sub":
                     let content = try convertElement(childElement)
-                    result += "~\(content)"
+                    result += "<sub>\(content)</sub>"
 
                 // Mark/highlight - render with markers
                 case "mark":
@@ -325,33 +325,27 @@ public class HTMLToMarkdownConverter {
     private func convertTable(_ element: Element) throws -> String {
         var result = "\n"
         var rows: [[String]] = []
-        var headerRowCount = 0
 
         // Get all rows from thead and tbody
         let allRows = try element.select("tr")
 
         for row in allRows {
             var cells: [String] = []
-            let thCells = try row.select("th")
-            let isHeaderRow = row.parent()?.tagName().lowercased() == "thead"
-                || !thCells.isEmpty()
 
             // Get th and td cells
             for cell in row.children() {
                 let tagName = cell.tagName().lowercased()
                 if tagName == "th" || tagName == "td" {
                     let content = try convertElement(cell)
                         .replacingOccurrences(of: "\n", with: " ")
+                        .replacingOccurrences(of: "|", with: "\\|") // Escape pipes for Markdown tables
                         .trimmingCharacters(in: .whitespaces)
                     cells.append(content)
                 }
             }
 
             if !cells.isEmpty {
                 rows.append(cells)
-                if isHeaderRow && headerRowCount == 0 {
-                    headerRowCount = 1
-                }
             }
         }
 

V2er/Sources/RichView/Renderers/MarkdownRenderer.swift

@@ -384,8 +384,8 @@ public class MarkdownRenderer {
                 break
             }
 
-            // Skip separator row (| --- | --- |)
-            if line.contains("---") {
+            // Skip separator row (| --- | --- | or with colons for alignment)
+            if line.range(of: #"^\|\s*(:?-+:?)\s*(\|\s*(:?-+:?)\s*)*\|$"#, options: .regularExpression) != nil {
                 index += 1
                 continue
             }

V2erTests/RichView/HTMLToMarkdownConverterTests.swift

@@ -274,6 +274,18 @@ class HTMLToMarkdownConverterTests: XCTestCase {
         XCTAssertTrue(markdown.contains("数据同步"))
     }
 
+    func testTableWithPipeInContent() throws {
+        let html = """
+        <table>
+            <tr><th>Option</th><th>Description</th></tr>
+            <tr><td>A | B</td><td>Choose A or B</td></tr>
+        </table>
+        """
+        let markdown = try converter.convert(html)
+        // Pipes should be escaped in cell content
+        XCTAssertTrue(markdown.contains("A \\| B"))
+    }
+
     // MARK: - Strikethrough Tests
 
     func testDelTagConversion() throws {
@@ -299,27 +311,27 @@ class HTMLToMarkdownConverterTests: XCTestCase {
     func testUnderlineTagConversion() throws {
         let html = "<u>Underlined text</u>"
         let markdown = try converter.convert(html)
-        XCTAssertTrue(markdown.contains("_Underlined text_"))
+        XCTAssertTrue(markdown.contains("<u>Underlined text</u>"))
     }
 
     func testInsTagConversion() throws {
         let html = "<ins>Inserted text</ins>"
         let markdown = try converter.convert(html)
-        XCTAssertTrue(markdown.contains("_Inserted text_"))
+        XCTAssertTrue(markdown.contains("<u>Inserted text</u>"))
     }
 
     // MARK: - Superscript/Subscript Tests
 
     func testSuperscriptConversion() throws {
         let html = "x<sup>2</sup>"
         let markdown = try converter.convert(html)
-        XCTAssertTrue(markdown.contains("^2"))
+        XCTAssertTrue(markdown.contains("<sup>2</sup>"))
     }
 
     func testSubscriptConversion() throws {
         let html = "H<sub>2</sub>O"
         let markdown = try converter.convert(html)
-        XCTAssertTrue(markdown.contains("~2"))
+        XCTAssertTrue(markdown.contains("<sub>2</sub>"))
     }
 
     // MARK: - Mark/Highlight Tests