fix(gateway): preserve case-sensitive chat IDs in DeliveryTarget.parse

Fixes NousResearch/hermes-agent#11768

Root cause: target.strip().lower() was lowercasing the entire target string,
corrupting case-sensitive chat IDs like Slack C123ABC and Matrix !RoomABC.

Fix: Only lowercase the platform prefix for case-insensitive matching;
preserve the original case for chat_id and thread_id values.

tests/gateway/test_delivery.py

@@ -65,4 +65,62 @@ class TestTargetToStringRoundtrip:
         assert reparsed.chat_id == "999"
 
 
+class TestCaseSensitiveChatIdParsing:
+    """Test that chat IDs preserve their original case (issue #11768)."""
+    
+    def test_slack_uppercase_chat_id_preserved(self):
+        """Slack channel IDs like C123ABC should preserve case."""
+        target = DeliveryTarget.parse("slack:C123ABC")
+        assert target.platform == Platform.SLACK
+        assert target.chat_id == "C123ABC"  # Should NOT be lowercased to c123abc
+        assert target.is_explicit is True
+    
+    def test_slack_chat_id_with_thread_preserved(self):
+        """Slack channel:thread IDs should preserve case."""
+        target = DeliveryTarget.parse("slack:C123ABC:thread123")
+        assert target.platform == Platform.SLACK
+        assert target.chat_id == "C123ABC"
+        assert target.thread_id == "thread123"
+    
+    def test_matrix_room_id_preserved(self):
+        """Matrix room IDs like !RoomABC:example.org should preserve case.
+        
+        Note: Matrix room IDs contain colons (e.g., !RoomABC:example.org).
+        Due to the platform:chat_id:thread_id format, these are parsed as
+        chat_id=!RoomABC and thread_id=example.org. This is a known limitation
+        of the current format. The fix preserves case but doesn't change the
+        parsing structure.
+        """
+        target = DeliveryTarget.parse("matrix:!RoomABC:example.org")
+        assert target.platform == Platform.MATRIX
+        # The room ID is split at the first colon after the platform prefix
+        # This is a format limitation - the case is preserved but the structure is split
+        assert target.chat_id == "!RoomABC"
+        assert target.thread_id == "example.org"
+    
+    def test_mixed_case_chat_id_roundtrip(self):
+        """Mixed-case chat IDs should survive parse-to_string roundtrip."""
+        original = "telegram:ChatId123ABC"
+        target = DeliveryTarget.parse(original)
+        s = target.to_string()
+        reparsed = DeliveryTarget.parse(s)
+        assert reparsed.chat_id == "ChatId123ABC"
+
+
+class TestPlatformNameCaseInsensitivity:
+    """Test that platform names are case-insensitive."""
+    
+    def test_uppercase_platform_name(self):
+        """Platform names should be case-insensitive."""
+        target = DeliveryTarget.parse("TELEGRAM:12345")
+        assert target.platform == Platform.TELEGRAM
+        assert target.chat_id == "12345"
+    
+    def test_mixed_case_platform_name(self):
+        """Mixed-case platform names should work."""
+        target = DeliveryTarget.parse("TeleGram:12345")
+        assert target.platform == Platform.TELEGRAM
+        assert target.chat_id == "12345"
+
+