feat: add retriever, trace and session

[namrataghadi-galileo]

Agent Control events can apply to LLM calls, tool calls, retriever calls, traces, or sessions. The SDK previously accepted only llm_call and tool_call, so the other supported values could fail enum conversion before a control span was emitted. This change adds retriever_call, trace_call, and session_call while preserving the existing values, extends the control span model and OpenAPI contract, and preserves applies_to and trace/session/parent correlation through OTEL conversion.

Tests

• Added coverage for all five supported applies_to values in the bridge and OTEL conversion paths.
• Focused tests: poetry run pytest tests/test_agent_control.py tests/test_agent_control_bridge.py tests/test_attribute_mapping.py tests/test_span_converter.py -q (133 passed).

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[namrataghadi-galileo]

I have read the CLA Document and I hereby sign the CLA

[namrataghadi-galileo]

recheck

[namrataghadi-galileo]

/recheck

[namrataghadi-galileo]

I have read the CLA Document and I hereby accept the CLA