chore: add ruff T20 lint rule to prevent prints in core modules

- Enable T20 (flake8-print) for all Python files
- Exclude scripts/, tools/, and .mindmodel/examples/ where
  stdout output is acceptable

Completes U6 of P2-001 (replace print with logging)

pyproject.toml

@@ -26,3 +26,12 @@ dev = [
     "pytest>=9.0.2",
     "pyright>=1.1.408",
 ]
+
+[tool.ruff.lint]
+select = ["T20"]
+ignore = []
+
+[tool.ruff.lint.per-file-ignores]
+"scripts/*" = ["T20"]
+"tools/*" = ["T20"]
+".mindmodel/examples/*" = ["T20"]