fix(telegram): catch orphaned single-letter TLD patterns

When text like 'R&D.md' doesn't match the main file pattern (because &
breaks the character class), the 'D.md' part can still be auto-linked
by Telegram as a domain (https://d.md/).

Add second pass to catch orphaned TLD patterns like 'D.md', 'R.io', 'X.ai'
that follow non-alphanumeric characters and wrap them in <code> tags.

Pattern: ([^a-zA-Z0-9]|^)([A-Za-z]\.(?:extensions))(?=[^a-zA-Z0-9/]|$)

Tests added:
- 'wraps orphaned TLD pattern after special character' (R&D.md → R&<code>D.md</code>)
- 'wraps orphaned single-letter TLD patterns' (X.ai, R.io)

src/telegram/format.ts

@@ -216,6 +216,20 @@ export function wrapFileReferencesInHtml(html: string): string {
     return `${prefix}<code>${escapeHtml(filename)}</code>`;
   });
 
+  // Second pass: catch orphaned single-letter TLD patterns (e.g., 'D.md' in 'R&D.md')
+  // These can be auto-linked by Telegram as domains
+  const orphanedTldPattern = new RegExp(
+    `([^a-zA-Z0-9]|^)([A-Za-z]\\.(?:${extensionsPattern}))(?=[^a-zA-Z0-9/]|$)`,
+    "g",
+  );
+  result = result.replace(orphanedTldPattern, (m, prefix, tld) => {
+    // Skip if already wrapped in a tag (check for < before or > after in context)
+    if (prefix === ">") {
+      return m;
+    }
+    return `${prefix}<code>${escapeHtml(tld)}</code>`;
+  });
+
   return result;
 }
 

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

@@ -278,12 +278,20 @@ describe("edge cases", () => {
     expect(wrapFileReferencesInHtml(input)).toBe(input);
   });
 
-  it("does not match filenames with special characters", () => {
-    // The regex only matches [a-zA-Z0-9_.\\-./] so & breaks the pattern
+  it("wraps orphaned TLD pattern after special character", () => {
+    // R&D.md - the & breaks the main pattern, but D.md could be auto-linked
+    // So we wrap the orphaned D.md part to prevent Telegram linking it
     const input = "R&D.md";
     const result = wrapFileReferencesInHtml(input);
-    // Not wrapped because & is not in the allowed character class
-    expect(result).toBe(input);
+    expect(result).toBe("R&<code>D.md</code>");
+  });
+
+  it("wraps orphaned single-letter TLD patterns", () => {
+    const result1 = wrapFileReferencesInHtml("X.ai is cool");
+    expect(result1).toContain("<code>X.ai</code>");
+
+    const result2 = wrapFileReferencesInHtml("Check R.io");
+    expect(result2).toContain("<code>R.io</code>");
   });
 
   it("does not match filenames containing angle brackets", () => {