Add official SDKs and LangGraph adapter

[AdamDiStefanoAI]

Summary

This PR adds the first official client/adaptation layer for the ACR control plane so teams can integrate at the action boundary without hand-rolling HTTP flows each time.

What changed

• add a typed Python SDK for agent registration, token issuance, health/readiness checks, and POST /acr/evaluate
• add bound agent sessions and decision-aware SDK errors
• add a real LangGraph/LangChain-style tool guard for synchronous and async tools
• refactor the sample agent to use the Python SDK instead of raw httpx calls
• add a shared gateway request/response model module used by both server and SDK code
• add a TypeScript SDK package that mirrors the same decision contract
• add SDK documentation and wire it into the README/orchestrator guidance

Validation

• PYTHONPATH=src:. pytest tests/test_sdk.py tests/test_gateway.py -q
• PYTHONPATH=src:. pytest tests -q --ignore=tests/integration
• python3 -m compileall src/acr/sdk src/acr/gateway/models.py examples/sample_agent/agent.py
• Node import/smoke check for sdks/typescript/dist/index.js

Notes

This PR intentionally leaves local workspace artifacts such as .coverage and var/ out of scope.