feat(providers/image): real gpt-image adapter (OpenAI Images API)

[wesleysimplicio]

Context

GptImageProvider at lib/providers/image.ts:40-42 is a mock. Per ROUTING-MATRIX.md, gpt-image is the default for quote cards, carousels, inpaint, and before/after — anywhere typography precision matters.

Goal

Real adapter calling OpenAI's images.generate (and images.edit for inpaint).

Acceptance criteria

• Adapter uses openai SDK (gpt-image-1 model)
• Maps aspect (1:1/4:5/9:16/16:9) to OpenAI sizes (1024x1024, 1024x1536, etc.) — fallback to closest supported with warning
• Supports n (number of variants) and transparent_background flag (passed by gpt-image-prompt-builder skill)
• Downloads bytes and saves to outputs/<client>/<date>/<piece-id>/<slot>-<seed>.png
• Returns real paths in output: string[]
• Real cost_usd from OpenAI pricing table (use shared lib/providers/cost.ts)
• Retry + timeout via shared policy
• Skipped when DRY_RUN=true
• E2E spec with mocked HTTP

Files

• lib/providers/image.ts:40-42
• .skills/gpt-image-prompt-builder/SKILL.md (no code change — read-only reference)

Depends on

• #provider-mocks-isolation, #policy-module

[wesleysimplicio]

Closed after PR #40 follow-up stabilization in commit f40b58d. Current main passes npm run typecheck and npm run test:e2e (119 Playwright specs green), and this tracker item is being retired per repository cleanup.