Restore green CI on main: ruff B905 (zip strict=) from 6db5c2b3 blocks the quality job

Observed by on-call after the #382 merge push (d7e53f5f, CI run 35010874544) and confirmed pre-existing.

Evidence

• Job quality fails: ruff B905 zip() without explicit strict= at courses/tests/test_course_illustrations.py:127. Reproduced locally at d7e53f5f with the exact CI command. Introduced by 6db5c2b3 (pushed 18:11Z); quality passed at the prior head 55a400c7 (15:56Z).
• Because the quality contract aborts on first failure, django/playwright were cancelled at b297191d and d7e53f5f. Deploy Dev verify-ci failed, deploy skipped.
• Independent pre-existing red: at 55a400c7 (quality green), django failed with failures=16, errors=1 and playwright failed (accessibility/article-parity among them). Attribution of those to introducing commits is still open; do not treat them as acceptable.

Acceptance criteria

• B905 fixed (strict=True; the zipped literals are equal-length) and the full quality contract passes locally, not just to the first failure
• typecheck and format-check targets re-run clean (separate assert is not None narrowing and reflow fixes are in flight in the shared checkout)
• push to main re-observed: quality, django, playwright jobs all green or each remaining failure attributed to an owning issue
• Deploy Dev goes green at the fixed head

Fix is in progress in the shared main checkout (uncommitted at time of filing); commit with Refs #N pointing at this issue.

Start at courses/tests/test_course_illustrations.py:127 and inspect the quality job output for the B905 failure. Re-run the repository's quality, typecheck, and format-check targets, then verify quality, django, playwright, and Deploy Dev at the fixed main head. Done means the zip warning is resolved and any remaining failures are attributed to owning issues.