Add LangGraph and CrewAI external agents via Entire Adapter

[suhaanthayyil]

Summary

Adds official external-agent entries for LangGraph and CrewAI using the published Python package entire-adapter==0.2.1.

What changed

• Adds entire-agent-langgraph and entire-agent-crewai wrappers.
• Uses the existing external-agent protocol: info, detect, parse-hook, transcript helpers, hook lifecycle commands, hook install state, and session round trips.
• Updates e2e build discovery so non-Go agents with mise.toml can participate in lifecycle tests.
• Adds deterministic LangGraph lifecycle coverage without requiring live LLM credentials.
• Adds optional CrewAI smoke coverage gated by CREWAI_E2E=1.

Validation

• mise run build agents/entire-agent-langgraph
• mise run build agents/entire-agent-crewai
• mise run test agents/entire-agent-langgraph
• mise run test agents/entire-agent-crewai
• mise exec -- external-agents-tests verify agents/entire-agent-langgraph/entire-agent-langgraph
• mise exec -- external-agents-tests verify agents/entire-agent-crewai/entire-agent-crewai
• E2E_AGENT=langgraph mise run test:e2e:lifecycle
• CREWAI_E2E=1 E2E_AGENT=crewai mise run test:e2e:lifecycle
• mise run test:ci
• mise run build
• gofmt -l .
• mise exec -- golangci-lint run from e2e/

Adapter package validation before this PR:

• python -m pytest -q
• ENTIRE_E2E=1 python -m pytest tests/e2e -q
• python -m build
• python -m twine check dist/*