[codex] harden python mcp server starter

[heznpc]

Summary

• tighten package metadata and console-script startup so installed runs use the tested wrapper
• make MCP stdio startup explicit and normalize blank-looking tool/prompt inputs
• add runtime contract tests and align README/CI commands with the actual validation surface

Verification

• .venv/bin/python -m pytest -v --cov=my_mcp_server --cov-report=term-missing --cov-fail-under=70
• .venv/bin/python -m ruff check .
• .venv/bin/python -m ruff format --check .
• .venv/bin/python -m mypy src/
• .venv/bin/python -m build
• .venv/bin/pip-audit . --strict
• .venv/bin/pip-licenses --fail-on="GPL-2.0;GPL-3.0;AGPL-3.0"
• printf "" | .venv/bin/python -m my_mcp_server
• printf "" | .venv/bin/my-mcp-server