Test coverage: HTTP API and api/cli (farm/api)

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Context

FastAPI / WebSocket code under farm/api/ is excluded from the coverage report in .coveragerc while the repo enforces a 90% gate on the simulation core.

This issue tracks API-layer test coverage (controllers, server wiring, CLI entrypoints that live under api).

Scope (paths)

• farm/api/server.py
• farm/api/simulation_controller.py
• farm/api/experiment_controller.py
• farm/api/analysis_controller.py
• farm/api/cli.py
• (Examples under farm/api/examples.py are already omitted at [run]; tests can still reference patterns from there.)

Suggested approach

• Use httpx.AsyncClient + ASGITransport or Starlette/FastAPI TestClient against the ASGI app.
• Mock long-running simulation work where needed; keep tests deterministic.
• Cover WebSocket handlers with short-lived connections and mocked backends where practical.

Acceptance criteria

• Integration-style tests marked appropriately if they need DB or network fakes.
• Trim .coveragerc [report] omit for files that reach stable coverage without breaking --cov-fail-under=90.