Improve regex to prevent double-formatting already-formatted links

Co-authored-by: ricardoV94 <[email protected]>

Author: Copilot

scripts/publish_release_notes_to_discourse.py

@@ -62,8 +62,9 @@ def format_release_content(config: dict[str, str]) -> tuple[str, str]:
 
     # Format PR links in the release body
     # Replace https://github.com/pymc-devs/pymc/pull/123 with [#123](https://github.com/pymc-devs/pymc/pull/123)
+    # Use negative lookbehind to avoid formatting already-formatted links
     release_body = re.sub(
-        r'https://github\.com/pymc-devs/pymc/pull/(\d+)',
+        r'(?<!\()\bhttps://github\.com/pymc-devs/pymc/pull/(\d+)\b',
         r'[#\1](\g<0>)',
         config["RELEASE_BODY"]
     )

scripts/test_publish_release_notes.py

@@ -125,3 +125,27 @@ def test_release_structure(self):
         assert "**Repository:** [pymc-devs/pymc](https://github.com/pymc-devs/pymc)" in content
         assert "**Release Page:** https://github.com/pymc-devs/pymc/releases/tag/v1.2.3" in content
         assert "[#999](https://github.com/pymc-devs/pymc/pull/999)" in content
+
+    def test_already_formatted_links_not_double_formatted(self):
+        """Test that already-formatted PR links are not double-formatted."""
+        release_body = """Some changes:
+* Already formatted: [#123](https://github.com/pymc-devs/pymc/pull/123)
+* Raw link: https://github.com/pymc-devs/pymc/pull/456
+"""
+
+        config = {
+            "RELEASE_TAG": "v1.0.0",
+            "REPO_NAME": "pymc-devs/pymc",
+            "RELEASE_BODY": release_body,
+            "RELEASE_URL": "https://github.com/pymc-devs/pymc/releases/tag/v1.0.0",
+        }
+
+        title, content = format_release_content(config)
+
+        # Already formatted link should remain unchanged
+        assert "[#123](https://github.com/pymc-devs/pymc/pull/123)" in content
+        # Should NOT be double-formatted
+        assert "[#123]([#123](https://github.com/pymc-devs/pymc/pull/123))" not in content
+        
+        # Raw link should be formatted
+        assert "[#456](https://github.com/pymc-devs/pymc/pull/456)" in content