Finish the review: spells/skills rulebook fidelity + test-quality pass

[StreamDemon]

Three review lenses never completed (session limits — see docs/reviews/2026-07-03-rules-layer-review.md, PR #19):

1. Spells fidelity: verify every spell in spells.json (levels 1–4) against printed pp.197–206 — level assignment, P.P.E. cost, range, duration, damage/effect, saving throw — plus engine magic mechanics vs Principles of Magic pp.185–190. Partial mitigation: the LLW sweep verified all 17 Rift & Ley Line spell costs; P.P.E./spell-strength level-awareness was verified in PR feat(rules): character-sheet assembly — deriveSheet() #5.
2. Skills fidelity: verify all 39 catalog skills' base % / per-level / two-value entries against Skill Descriptions pp.304–329, and the selection rules pp.298–301.
3. Test-quality pass: coverage gaps, tautological assertions, wrong hardcoded expectations across the 7 test files.

Best done as targeted inline spot-checks (a few PDF pages at a time), ideally before or alongside #13.