fix: Timmy startup crashes and clean initialization

- Remove show_tool_calls kwarg (not in Agno 2.5.3), which crashed Agent.__init__
- Guard memory_search against top_k=None from model, return formatted string
- Skip Telegram/Discord startup silently when no token configured
- Replace placeholder MEMORY.md with proper structured hot memory document

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_agent.py

@@ -267,8 +267,8 @@ def test_create_timmy_includes_tools_for_large_model():
         assert kwargs["tools"] == [mock_toolkit]
 
 
-def test_create_timmy_show_tool_calls_false():
-    """show_tool_calls should always be False to prevent raw JSON in output."""
+def test_create_timmy_no_show_tool_calls():
+    """show_tool_calls must NOT be passed — Agno 2.5.3 doesn't support it."""
     with patch("timmy.agent.Agent") as MockAgent, \
          patch("timmy.agent.Ollama"), \
          patch("timmy.agent.SqliteDb"):
@@ -277,4 +277,4 @@ def test_create_timmy_show_tool_calls_false():
         create_timmy()
 
         kwargs = MockAgent.call_args.kwargs
-        assert kwargs["show_tool_calls"] is False
+        assert "show_tool_calls" not in kwargs