build: replace black and isort with ruff

ruff format keeps black's style at the same line length, and ruff
check covers import sorting plus pycodestyle and pyflakes. Three
comments and a test regex are wrapped to fit 79 columns.

pyproject.toml

@@ -42,10 +42,11 @@ build-backend = "hatchling.build"
 [dependency-groups]
 dev = ["pre-commit>=2.16.0", "pytest>=8.0"]
 
-[tool.black]
+[tool.ruff]
 line-length = 79
 
-[tool.isort]
-known_first_party = "pqcli"
-multi_line_output = 3
-include_trailing_comma = true
+[tool.ruff.lint]
+select = ["E", "F", "W", "I"]
+
+[tool.ruff.lint.isort]
+known-first-party = ["pqcli"]