Type modern server entry points

[branta42]

Summary

• add strict mypy coverage for the modern MCP/server entry points and adjacent HTTP/MCP CLI tests
• annotate MCP server construction and transport handling instead of leaving those paths untyped
• make CLI console-script tests resolve the repo-local .venv entrypoint so they pass consistently under and outside the quality gate

Testing

• JAVA_HOME=/usr/lib/jvm/java-21-openjdk-amd64 PATH=/usr/lib/jvm/java-21-openjdk-amd64/bin:/store2/scratch/rpradeep/castorini-monorepo/rank_llm/.venv/bin:$PATH .venv/bin/python scripts/quality_gate.py
• PATH=/store2/scratch/rpradeep/castorini-monorepo/rank_llm/.venv/bin:$PATH .venv/bin/python -m unittest test.test_cli_http test.test_cli_mcp
• .venv/bin/python -m mypy