Proposal: add an opt-in 16688 AI image provider #19

Problem

BeatDesign supports pluggable generation providers, but the 16688 Studio deployment needs an opt-in image-generation provider that can use NewAPI-compatible image generation and a configurable Gemini media gateway without changing upstream defaults.

Proposed scope

• register 16688 AI as an opt-in provider enabled only by the 16688 build mode
• support text-to-image through NewAPI and configurable Gemini media-gateway transports
• keep provider credentials server-side and encrypted in local SQLite
• preserve existing BeatAPI defaults, Canvas data, assets, generation history, and MCP behavior
• include a deployment profile for studio.16688.org

Non-goals

• login, payments, subscriptions, credits, admin, or RBAC modules
• reference-image editing through this provider stage
• video generation through this provider stage

Implementation

A working implementation is available in PR #18. It contains 11 commits across 54 files and keeps the provider opt-in.

Verification completed

• pnpm typecheck
• pnpm test (428 passing)
• pnpm i18n:check (632 keys in English, Chinese, and Japanese)
• pnpm build
• pnpm build:16688
• local browser smoke test at 390px and 648px widths
• MCP stdio handshake in the test suite

Credentialed/paid provider generation has not been run. Feedback is welcome on the provider boundary and whether the deployment profile should remain in the same PR.