fix: add CJS declarations for public exports

[sjungwon03]

Summary

• fixes Node16/CommonJS TypeScript TS1479 failures for TypeChain root, /langchain, /agent, and /typemcp static imports
• adds matching CJS runtime bundles (.cjs) and conditionally selected CommonJS declarations (.d.cts) while retaining existing ESM artifacts
• verifies all public entrypoint artifacts and package export conditions
• extends packed Node16 CommonJS consumer coverage to compile and execute root, LangChain, agent, and TypeMCP subpath imports with their declared peers
• updates current-release documentation to TypeChain 0.2.1 and TypeMCP 0.3.1

Verification

• npm run verify
• npm run verify:consumer
• npm run verify:publish
• npm audit --omit=dev --audit-level=low
• git diff --check

Closes #102

[sjungwon03-ai]

Reviewed the exact head 7a8d4d3. Verified nested import/require type conditions and matching CJS artifacts, packed Node16 CommonJS static-import compilation and runtime for root/langchain/agent/typemcp with declared peers, plus full CI and npm 12 readiness. No blocking findings.