Add unit tests for ToolService

[philippe-ths]

Parent

Part of #34

Goal

Verify tool execution paths including code generation, web search, and sandbox restrictions.

What to test

• Sandbox capability restrictions block disallowed operations
• Function CRUD (create, update, delete, retrieve)
• Web search request formation and response handling
• Code generation validation rejects unsafe or invalid output
• Sandbox timeout enforcement

[philippe-ths]

Tracked but deferred — leaving open for future work.