Evaluate GPT-Image-v2 for RPG card art consistency

## Context

ThursdAI 2026-04-23 covered **GPT-Image-v2**, a reasoning-based image model with character consistency and 360-degree equirectangular output. Relevant to HunterPath because:

- HunterPath has ongoing RPG card generation (per project history).
- Character consistency would let the same Hunter portrait appear on ability cards, loot cards, and flavor cards.
- Functional QR-code generation could enable physical-print card variants that link back to the app.

## Proposal

Run a quick evaluation: generate a small deck (5 cards) with GPT-Image-v2 versus whatever we currently use, compare for:

- Character consistency across the deck.
- Art style match to HunterPath's existing aesthetic.
- Cost and speed.

Create a decision doc and either adopt for future cards or archive.

This is lower priority than the primary work on HunterPath (zero test coverage, per plan), but worth a half-day evaluation when the opportunity arises.

## Links

- ThursdAI 2026-04-23: https://sub.thursdai.news/p/apr-23-openais-week-gpt-55-gpt-image
- OpenAI announcement: https://openai.com/index/introducing-chatgpt-images-2-0/