Add AGENTS.md with Cursor Cloud development instructions

[dlpe]

Adds AGENTS.md with development environment instructions for Cursor Cloud agents.

What's included

• Quick-reference commands for install, test, and build
• Key notes about the self-contained test suite (MockAgent + in-memory SQLite)
• Clarification that 17 skipped integration tests are expected (require live Ollama/API keys)
• Source layout and editable install behavior notes

Verification

• All 200 unit tests pass, 17 integration tests skipped as expected
• Hello-world demo exercising tool-calling, SQLAlchemy integration, and structured output all succeed

pytest_output.log
hello_world_demo.log

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