build: restore pylint to the quality checks

[farhan]

Important

Generated with Claude, then manually reviewed (both this PR description and the code commits).

Related

• Closes Restore pylint: ruff is not a drop-in replacement #289
• Follow-up to the pip-compile → uv modernization (Modernize Python repo: pyproject.toml + uv + semantic-release #251), which dropped pylint
• Linting strategy for Open edX Python repos: #289 comment

Summary

Restores pylint to the quality gate alongside ruff. Per #289, ruff is not a drop-in replacement for pylint — it does not run the edx_lint plugins and does not catch the class of issues (undefined attributes, type mismatches, etc.) that pylint does. Ruff stays responsible for style, imports, formatting, unused-import, and line-length; pylint is added back for the deeper static analysis.

Ruff / pylint ownership

Each check is owned by exactly one tool, so nothing is enforced twice:

• unused-import (F401) → ruff. It's auto-fixable via ruff check --fix, so pylint disables unused-import. The package __init__ re-exports use the explicit import X as X alias idiom (PEP 484), which ruff recognizes as intentional re-exports (no F401). This idiom is used instead of __all__ because Sphinx (built with -W) re-documents __all__ re-exports under every import path, producing duplicate-object and ambiguous-cross-reference warnings that fail the docs check — the alias idiom is not re-documented by autodoc, so docs stays green. pylint's useless-import-alias (C0414) is disabled since it is a false positive on this deliberate re-export idiom.
• line-length (E501 / C0301) → ruff. Ruff's E501 enforces the 120-char limit (its ignore list no longer skips E501); pylint's line-too-long (C0301) is disabled so the limit is checked in only one place. Ruff can auto-fix most long lines via ruff format; the few it can't (e.g. long f-strings) are split manually.

Everything else in ruff's select (E, W, F, I, B, C4, UP, DJ) stays active. This keeps pylint on its edx-lint defaults and mirrors how edx-platform runs the two tools side by side.

The change also renames the Makefile lint target to quality and removes now-redundant lint-amnesty / pylint: disable suppression comments (e.g. raise-missing-from, too-many-positional-arguments) that the restored config no longer flags.

Testing

tox -e quality passes end to end (ruff check, ruff format --check, pylint xblocks_contrib xblock_pdf), and tox -e docs builds cleanly with warnings-as-errors (-W). CI already runs uv run tox with both quality and docs in the matrix, so they run there automatically — no workflow change needed.

[kdmccormick]

thanks for the PR!

nit: do you mind changing the commit title to build: ... ? that way, if somebody squash-merges, we end up with the correct commit message title. The commit titles matter more now that we're using them as input to semantic releases.

[farhan]

@kdmccormick
Squashed & addressed, its available for next pass/merge