use claude haiku 4.5 for research agent (#1234)

- upgrade pydantic-ai to 1.1.0 (includes haiku 4.5 support)
- switch research agent from openai:gpt-4o to anthropic:claude-haiku-4-5
- haiku 4.5 provides faster, cheaper research with similar quality

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: zzstoatzz

examples/slackbot/src/slackbot/research_agent.py

@@ -42,7 +42,7 @@ def create_research_agent(
     """Create a specialized research agent for thorough information gathering."""
 
     agent = Agent[ResearchContext, ResearchFindings](
-        model=model or "openai:gpt-4o",
+        model=model or "anthropic:claude-haiku-4-5",
         deps_type=ResearchContext,
         output_type=ResearchFindings,
         system_prompt="""You are a specialized research agent for Prefect documentation and knowledge.