P0: scoring.json + score.ts composite score

[Doberjohn]

The transparent Deck Quality Score: a versioned config + a pure composite scorer.

Scope

• scoring.json default config (dimension weights + thresholds), versioned + snapshot-guarded like tuning.json (extends the /admin/tuning pattern).
• analysis/score.ts: scoreDeck(health, config) → { score (0–100), breakdown[], configVersion }, where score = Σ(weightᵢ × dimensionScoreᵢ) + archetypeCoherence − vulnerabilityPenalty.
• Every score returns a per-dimension breakdown (contribution + reason) — explainability is a hard requirement.

Tests: deterministic given config, version stamp present, breakdown contributions sum to the score.

Part of #450 · Deck Builder & Engine Score milestone.

[Doberjohn]

Delivered and merged into the deck-builder integration branch via #480 (not yet in production / master). Closing as complete; it rides to production when deck-builder later merges to master.