refactor(telegram): remove popular domain TLDs from file extension list

Remove .ai, .io, .tv, .fm from FILE_EXTENSIONS_WITH_TLD because:
- These are commonly used as real domains (x.ai, vercel.io, github.io)
- Rarely used as actual file extensions
- Users are more likely referring to websites than files

Keep: md, sh, py, go, pl (common file extensions, rarely intentional domains)
Keep: am, at, be, cc, co (less common as intentional domain references)

Update tests to reflect the change:
- Add test for supported extensions (.am, .at, .be, .cc, .co)
- Add test verifying popular TLDs stay as links

src/telegram/format.ts

@@ -24,24 +24,24 @@ function escapeHtmlAttr(text: string): string {
  * File extensions that share TLDs and commonly appear in code/documentation.
  * These are wrapped in <code> tags to prevent Telegram from generating
  * spurious domain registrar previews.
+ *
+ * Only includes extensions that are:
+ * 1. Commonly used as file extensions in code/docs
+ * 2. Rarely used as intentional domain references
+ *
+ * Excluded: .ai, .io, .tv, .fm (popular domain TLDs like x.ai, vercel.io, github.io)
  */
 const FILE_EXTENSIONS_WITH_TLD = new Set([
-  // High priority - commonly referenced in messages
-  "md", // Markdown (Moldova)
-  "go", // Go language
-  "py", // Python (Paraguay)
-  "pl", // Perl (Poland)
-  "ai", // Adobe Illustrator (Anguilla)
-  "sh", // Shell (Saint Helena)
-  // Medium priority - sometimes referenced
-  "io", // Tuvalu (often used for tech projects)
-  "tv", // Tuvalu (video files)
-  "fm", // Federated States of Micronesia (audio)
-  "am", // Armenia
-  "at", // Austria
-  "be", // Belgium
-  "cc", // Cocos Islands
-  "co", // Colombia
+  "md", // Markdown (Moldova) - very common in repos
+  "go", // Go language - common in Go projects
+  "py", // Python (Paraguay) - common in Python projects
+  "pl", // Perl (Poland) - common in Perl projects
+  "sh", // Shell (Saint Helena) - common for scripts
+  "am", // Automake files (Armenia)
+  "at", // Assembly (Austria)
+  "be", // Backend files (Belgium)
+  "cc", // C++ source (Cocos Islands)
+  "co", // Configuration (Colombia)
 ]);
 
 /** Detects when markdown-it linkify auto-generated a link from a bare filename (e.g. README.md → http://README.md) */

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

@@ -191,12 +191,25 @@ describe("edge cases", () => {
     expect(result).toBe("README.md");
   });
 
-  it("wraps all TLD extensions (.ai, .io, .tv, .fm)", () => {
-    const result = markdownToTelegramHtml("logo.ai and app.io and video.tv and audio.fm");
-    expect(result).toContain("<code>logo.ai</code>");
-    expect(result).toContain("<code>app.io</code>");
-    expect(result).toContain("<code>video.tv</code>");
-    expect(result).toContain("<code>audio.fm</code>");
+  it("wraps supported TLD extensions (.am, .at, .be, .cc, .co)", () => {
+    const result = markdownToTelegramHtml(
+      "Makefile.am and code.at and app.be and main.cc and config.co",
+    );
+    expect(result).toContain("<code>Makefile.am</code>");
+    expect(result).toContain("<code>code.at</code>");
+    expect(result).toContain("<code>app.be</code>");
+    expect(result).toContain("<code>main.cc</code>");
+    expect(result).toContain("<code>config.co</code>");
+  });
+
+  it("does not wrap popular domain TLDs (.ai, .io, .tv, .fm)", () => {
+    // These are commonly used as real domains (x.ai, vercel.io, github.io)
+    const result = markdownToTelegramHtml("Check x.ai and vercel.io and app.tv and radio.fm");
+    // Should be links, not code
+    expect(result).toContain('<a href="http://x.ai">');
+    expect(result).toContain('<a href="http://vercel.io">');
+    expect(result).toContain('<a href="http://app.tv">');
+    expect(result).toContain('<a href="http://radio.fm">');
   });
 
   it("does not wrap non-TLD extensions", () => {
@@ -287,11 +300,12 @@ describe("edge cases", () => {
   });
 
   it("wraps orphaned single-letter TLD patterns", () => {
-    const result1 = wrapFileReferencesInHtml("X.ai is cool");
-    expect(result1).toContain("<code>X.ai</code>");
+    // Use extensions still in the set (md, sh, py, go)
+    const result1 = wrapFileReferencesInHtml("X.md is cool");
+    expect(result1).toContain("<code>X.md</code>");
 
-    const result2 = wrapFileReferencesInHtml("Check R.io");
-    expect(result2).toContain("<code>R.io</code>");
+    const result2 = wrapFileReferencesInHtml("Check R.sh");
+    expect(result2).toContain("<code>R.sh</code>");
   });
 
   it("does not match filenames containing angle brackets", () => {