fix: log Ollama disconnections with specific error handling (#92)

- BaseAgent.run(): catch httpx.ConnectError/ReadError/ConnectionError,
  log 'Ollama disconnected: <error>' at ERROR level, then re-raise
- session.py: distinguish Ollama disconnects from other errors in
  chat(), chat_with_tools(), continue_chat() — return specific message
  'Ollama appears to be disconnected' instead of generic error
- 11 new tests covering all disconnect paths

src/timmy/agents/base.py

@@ -14,6 +14,7 @@ import logging
 from abc import ABC, abstractmethod
 from typing import Any
 
+import httpx
 from agno.agent import Agent
 from agno.models.ollama import Ollama
 
@@ -120,8 +121,15 @@ class BaseAgent(ABC):
         Returns:
             Agent response
         """
-        result = self.agent.run(message, stream=False)
-        response = result.content if hasattr(result, "content") else str(result)
+        try:
+            result = self.agent.run(message, stream=False)
+            response = result.content if hasattr(result, "content") else str(result)
+        except (httpx.ConnectError, httpx.ReadError, ConnectionError) as exc:
+            logger.error("Ollama disconnected: %s", exc)
+            raise
+        except Exception as exc:
+            logger.error("Agent run failed: %s", exc)
+            raise
 
         # Emit completion event
         if self.event_bus: