fix(telegram): clamp depth counters and add anchor tracking to orphaned pass

- Clamp depth counters at 0 for malformed HTML with stray closing tags
- Add anchor depth tracking to orphaned TLD pass to prevent wrapping
  inside link text (e.g., <a href="...">R&D.md</a>)
- 57 tests covering all edge cases

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/telegram/format.ts

@@ -187,13 +187,13 @@ export function wrapFileReferencesInHtml(html: string): string {
       return `${prefix}<code>${escapeHtml(filename)}</code>`;
     });
 
-    // Update tag depth
+    // Update tag depth (clamp at 0 for malformed HTML with stray closing tags)
     if (tagName === "code") {
-      codeDepth += isClosing ? -1 : 1;
+      codeDepth = isClosing ? Math.max(0, codeDepth - 1) : codeDepth + 1;
     } else if (tagName === "pre") {
-      preDepth += isClosing ? -1 : 1;
+      preDepth = isClosing ? Math.max(0, preDepth - 1) : preDepth + 1;
     } else if (tagName === "a") {
-      anchorDepth += isClosing ? -1 : 1;
+      anchorDepth = isClosing ? Math.max(0, anchorDepth - 1) : anchorDepth + 1;
     }
 
     // Add the tag itself
@@ -236,14 +236,16 @@ export function wrapFileReferencesInHtml(html: string): string {
     if (lastOpen > lastClose) {
       return m; // Inside a tag attribute
     }
-    // Skip if inside code/pre tags (count opens vs closes before offset)
+    // Skip if inside code/pre/anchor tags (count opens vs closes before offset)
     const textBefore = snapshot.slice(0, offset);
     const codeOpens = (textBefore.match(/<code/gi) || []).length;
     const codeCloses = (textBefore.match(/<\/code/gi) || []).length;
     const preOpens = (textBefore.match(/<pre/gi) || []).length;
     const preCloses = (textBefore.match(/<\/pre/gi) || []).length;
-    if (codeOpens > codeCloses || preOpens > preCloses) {
-      return m; // Inside code/pre content
+    const anchorOpens = (textBefore.match(/<a[\s>]/gi) || []).length;
+    const anchorCloses = (textBefore.match(/<\/a/gi) || []).length;
+    if (codeOpens > codeCloses || preOpens > preCloses || anchorOpens > anchorCloses) {
+      return m; // Inside code/pre/anchor content
     }
     return `${prefix}<code>${escapeHtml(tld)}</code>`;
   });

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

@@ -336,6 +336,27 @@ describe("edge cases", () => {
     expect(result).not.toContain("</code></code>");
   });
 
+  it("does not wrap orphaned TLD inside anchor link text", () => {
+    // R&D.md inside anchor text should NOT have D.md wrapped
+    const input = '<a href="https://example.com">R&D.md</a>';
+    const result = wrapFileReferencesInHtml(input);
+    expect(result).toBe(input);
+    expect(result).not.toContain("<code>D.md</code>");
+  });
+
+  it("handles malformed HTML with stray closing tags (negative depth)", () => {
+    // Stray </code> before content shouldn't break protection logic
+    // (depth should clamp at 0, not go negative)
+    const input = "</code>README.md<code>inside</code> after.md";
+    const result = wrapFileReferencesInHtml(input);
+    // README.md should be wrapped (codeDepth = 0 after clamping stray close)
+    expect(result).toContain("<code>README.md</code>");
+    // after.md should be wrapped (codeDepth = 0 after proper close)
+    expect(result).toContain("<code>after.md</code>");
+    // Should not have nested code tags
+    expect(result).not.toContain("<code><code>");
+  });
+
   it("does not wrap orphaned TLD inside href attributes", () => {
     // D.md inside href should NOT be wrapped
     const input = '<a href="http://example.com/R&D.md">link</a>';