verify(langgraph): installed constructor, MCP binding and descriptor APIs (§§8–10) #642

Summary

Verify LangGraph's installed framework APIs for docs/verified-apis.md §§8–10. This is a per-framework slice of #34; I am taking this work.

Scope

• Run the unchanged python/scripts/verify_frameworks.py --only langgraph and --emit-verified against installed distributions.
• Independently probe the MCP binding and descriptor attributes using real installed classes and record exact kwargs, distribution versions, date, and captured output.
• Update only claims supported by the evidence, explicitly distinguishing offline signatures/attributes from live gateway behavior. Preserve all existing _verify.blocked(...) guards.
• Record any demonstrated incompatibility in §8.1; do not hide it with dependency ceilings or a weakened check.
• Run the framework-free unit gate and required pre-PR checks. Submit one PR for this framework into develop.

Acceptance

Reproducible executable evidence, truthful ledger rows, and synchronized framework documentation. Runtime, live gateway, and conformance promotion are not implied by offline verification. Parent #34 remains open for the remaining framework/live acceptance criteria.

Please assign the Verification milestone and appropriate verification/testing labels (fork contributor).