Implement Snap metadata extraction via UI-TARS

[BryanChasko]

Agent Task

Agent: ellow-gander-mechanic
Depends on: Create snap-classify.yaml sub-recipe
Branch: feat/snap-metadata-extraction
Source: specs/marvel-snap-pipeline/tasks.md

Acceptance Criteria

• Extract cards played, locations, turn number, energy, score, opponent
• Output structured JSON conforming to game record schema
• Include per-field confidence scores
• Flag uncertain fields, never fabricate

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