feat: Add code-first prompt templates for agent code execution

This commit adds optimized prompt templates that guide agents to write
code instead of making direct tool calls, enabling the Code Execution
with MCP approach for massive token reduction.

New features:
- Code execution prompts module in terraphim_multi_agent
- TypeScript system prompt with complete MCP tool documentation
- Python system prompt with type-annotated tool usage
- Task analysis for automatic execution mode selection
- Anti-patterns guidance to avoid token waste
- Examples showing in-environment data processing

Key capabilities:
- Agents can now be configured for code-first behavior
- Prompts emphasize processing data in-environment
- Return only minimal results (not raw data)
- Parallel execution patterns for efficiency
- Error handling and robustness guidelines

This completes the foundation for Code Execution with MCP:
1. ✅ MCP code generation (TypeScript/Python wrappers)
2. ✅ Runtime bridge for VM environments
3. ✅ Code-first prompts for agents
4. 🔲 VM integration (next phase)
5. 🔲 End-to-end testing (next phase)

Expected token reduction: 98% for complex workflows

Author: claude

crates/terraphim_multi_agent/src/lib.rs

@@ -35,6 +35,7 @@ pub mod genai_llm_client;
 pub mod history;
 pub mod llm_types;
 pub mod prompt_sanitizer;
+pub mod prompts;
 pub mod vm_execution;
 // pub mod llm_client;      // Disabled - uses rig-core
 // pub mod simple_llm_client; // Disabled - uses rig-core