feat: enforce narrative fair-play checks

[caoergou]

Summary

• add opt-in required / optional PuzzleGraph clue layers, required-node solve proofs, and warning-only diagnostics for incomplete layers, silent progress, and timer-delivered clues
• add explicit content-pack narrative metadata with Chekhov's-gun and red-herring validation, including stable warning codes and real payoff-location checks
• mirror player file:update and file:unlock events into the headless solver filesystem before trigger evaluation
• add lint-clean Patterns 19–24 for truth archives, challenge-the-reader checkpoints, false-to-true solutions, unreliable narration, clue-in-noise newspapers, and midpoint injections

Validation

• npm run scenario:ci (24 pattern fixtures, zero errors and zero warnings)
• npm run schema:check
• npm run typecheck:strict
• npm run lint
• npm run knip
• npm run scenario:build
• npm run build:lib
• npm run size:check
• focused Vitest regression suites: 61 tests passed

Closes #267