fix(telegram): use regex literal and depth counters for tag tracking

Code review fixes:
1. Replace RegExp constructor with regex literal for autoLinkedAnchor
   - Avoids double-escaping issues with \s
   - Uses backreference \1 to match href=label pattern directly

2. Replace boolean toggles with depth counters for tag nesting
   - codeDepth, preDepth, anchorDepth track nesting levels
   - Correctly handles nested tags like <pre><code>...</code></pre>
   - Prevents wrapping inside any level of protected tags

Add 4 tests for edge cases:
- Nested code tags (depth tracking)
- Multiple anchor tags in sequence
- Auto-linked anchor with backreference match
- Anchor with different href/label (no match)

src/telegram/format.ts

@@ -137,12 +137,9 @@ export function wrapFileReferencesInHtml(html: string): string {
   const extensionsPattern = Array.from(FILE_EXTENSIONS_WITH_TLD).join("|");
 
   // Safety-net: de-linkify auto-generated anchors where href="http://<label>" (defense in depth for textMode: "html")
-  const autoLinkedAnchor = new RegExp(`<a\\s+href="https?://([^"]+)"\\s*>([^<]+)</a>`, "gi");
-  html = html.replace(autoLinkedAnchor, (_match, href: string, label: string) => {
-    if (href !== label) {
-      return _match;
-    }
-    if (!isAutoLinkedFileRef(`http://${href}`, label)) {
+  const autoLinkedAnchor = /<a\s+href="https?:\/\/([^"]+)"[^>]*>\1<\/a>/gi;
+  html = html.replace(autoLinkedAnchor, (_match, label: string) => {
+    if (!isAutoLinkedFileRef(`http://${label}`, label)) {
       return _match;
     }
     return `<code>${label}</code>`;
@@ -152,10 +149,10 @@ export function wrapFileReferencesInHtml(html: string): string {
     "gi",
   );
 
-  // Track if we're inside tags that should not be modified
-  let inCode = false;
-  let inPre = false;
-  let inAnchor = false;
+  // Track nesting depth for tags that should not be modified
+  let codeDepth = 0;
+  let preDepth = 0;
+  let anchorDepth = 0;
   let result = "";
   let lastIndex = 0;
 
@@ -173,7 +170,7 @@ export function wrapFileReferencesInHtml(html: string): string {
     const textBefore = html.slice(lastIndex, tagStart);
     result += textBefore.replace(filePattern, (m, prefix, filename) => {
       // Skip if inside protected tags or if it's a URL
-      if (inCode || inPre || inAnchor) {
+      if (codeDepth > 0 || preDepth > 0 || anchorDepth > 0) {
         return m;
       }
       if (filename.startsWith("//")) {
@@ -185,13 +182,13 @@ export function wrapFileReferencesInHtml(html: string): string {
       return `${prefix}<code>${filename}</code>`;
     });
 
-    // Update tag state
+    // Update tag depth
     if (tagName === "code") {
-      inCode = !isClosing;
+      codeDepth += isClosing ? -1 : 1;
     } else if (tagName === "pre") {
-      inPre = !isClosing;
+      preDepth += isClosing ? -1 : 1;
     } else if (tagName === "a") {
-      inAnchor = !isClosing;
+      anchorDepth += isClosing ? -1 : 1;
     }
 
     // Add the tag itself
@@ -202,7 +199,7 @@ export function wrapFileReferencesInHtml(html: string): string {
   // Process remaining text
   const remainingText = html.slice(lastIndex);
   result += remainingText.replace(filePattern, (m, prefix, filename) => {
-    if (inCode || inPre || inAnchor) {
+    if (codeDepth > 0 || preDepth > 0 || anchorDepth > 0) {
       return m;
     }
     if (filename.startsWith("//")) {

src/telegram/format.wrap-md.test.ts

@@ -250,4 +250,31 @@ describe("edge cases", () => {
     expect(result).toContain("<code>README.MD</code>");
     expect(result).toContain("<code>SCRIPT.PY</code>");
   });
+
+  it("handles nested code tags (depth tracking)", () => {
+    // Nested <code> inside <pre> - should not wrap inner content
+    const input = "<pre><code>README.md</code></pre> then script.py";
+    const result = wrapFileReferencesInHtml(input);
+    expect(result).toBe("<pre><code>README.md</code></pre> then <code>script.py</code>");
+  });
+
+  it("handles multiple anchor tags in sequence", () => {
+    const input =
+      '<a href="https://a.com">link1</a> README.md <a href="https://b.com">link2</a> script.py';
+    const result = wrapFileReferencesInHtml(input);
+    expect(result).toContain("</a> <code>README.md</code> <a");
+    expect(result).toContain("</a> <code>script.py</code>");
+  });
+
+  it("handles auto-linked anchor with backreference match", () => {
+    // The regex uses \1 backreference - href must equal label
+    const input = '<a href="http://README.md">README.md</a>';
+    expect(wrapFileReferencesInHtml(input)).toBe("<code>README.md</code>");
+  });
+
+  it("preserves anchor when href and label differ (no backreference match)", () => {
+    // Different href and label - should NOT de-linkify
+    const input = '<a href="http://other.md">README.md</a>';
+    expect(wrapFileReferencesInHtml(input)).toBe(input);
+  });
 });