[nikbpetrov]

On top of #340

Only thing to pay attention to, @houtanb , is the jupyter notebooks - minor formatting changes.

===

Swap the four lint/format tools for a single exact-pinned ruff, configured in pyproject.toml with a ruleset that mirrors the previous setup: E/W/F/B/I/D with E203, E701 and bugbear's opt-in B9xx ignored, pycodestyle max-line-length = 110 standing in for B950, pep257 docstrings, and tests exempt from D as they were under pydocstyle. setup.cfg is gone. Markdown files are excluded from ruff format so fenced code blocks stay untouched, as before.

make lint keeps its name and its MAKE_LINT_ERROR_OUT=1 check mode, so the CI workflow is unchanged. ruff check --fix runs before ruff format, as ruff recommends.

Code changes are mechanical:

• # noqa: B950 becomes # noqa: E501, or is dropped where ruff reports the directive unused. The 46 in sources/_metadata.py were leftovers on closing parentheses of lines black had already wrapped. # flake8: noqa: B950 used to exempt the whole file from flake8; # ruff: noqa: E501 only exempts line length, and those files are otherwise clean.
• # noqa: E402 after sys.path edits is dropped because ruff allows imports there.
• The ruff format pass, including the PEP 758 except A, B: form from target-version = "py314".

AST is byte-identical, so no parity job runs are needed.

Closes #121

[houtanb]

3 issues found by claude:

  1. make lint stops before formatting (Makefile:58). ruff check --fix fails on a long line it can't fix, so ruff format
     never runs to wrap it. I reproduced this. The fix is to run ruff check --fix --exit-zero, then ruff format, then
     ruff check.
  2. A file-wide noqa sits mid-file (src/sources/wikipedia.py:954). # ruff: noqa: E501 turns off the line-length check
     for the whole module, not just the hash mapping below it. Use per-line # noqa: E501 or a per-file-ignores entry
     instead.
  3. AGENTS.md has the wrong line length (AGENTS.md:106). It says 100, but ruff check enforces 110 (pyproject.toml:30).
     Only ruff format targets 100.

[nikbpetrov]

3 issues found by claude:

  1. make lint stops before formatting (Makefile:58). ruff check --fix fails on a long line it can't fix, so ruff format
     never runs to wrap it. I reproduced this. The fix is to run ruff check --fix --exit-zero, then ruff format, then
     ruff check.
  2. A file-wide noqa sits mid-file (src/sources/wikipedia.py:954). # ruff: noqa: E501 turns off the line-length check
     for the whole module, not just the hash mapping below it. Use per-line # noqa: E501 or a per-file-ignores entry
     instead.
  3. AGENTS.md has the wrong line length (AGENTS.md:106). It says 100, but ruff check enforces 110 (pyproject.toml:30).
     Only ruff format targets 100.

1. makes sense
2. sure, though that's on parity with the old flake8 behaviour and is scoped to only 1-2 files; in any case, i've now centralized the logic using per-file-ignores in pyproject.toml to make it clearer
3. explaind in pyproject.toml:

[tool.ruff.lint.pycodestyle]
# E501 at 110 reproduces bugbear's B950 (line-length + 10 %).
max-line-length = 110

(applies only to docs, not to code, which still uses line-length = 100; no further action taken here)