U1: Scaffold Next.js, Convex, and test harness

[breadback00-dev]

What is the work

Establish the root application foundation for Bristol Carousel: a TypeScript Next.js App Router app, Convex client wiring, and the initial Vitest, Convex test, Sharp-compatible Node test, and Playwright harnesses.

Planned areas:

• package.json
• app/layout.tsx
• app/page.tsx
• app/ConvexClientProvider.tsx
• convex/
• vitest.config.ts
• playwright.config.ts
• tests/e2e/

Why does it matter

The repo is currently documentation-only. Every later unit depends on having a working app shell, Convex integration, and reliable test commands before product behavior can be added safely.

What does done mean

• A root Next.js App Router app exists and renders locally.
• Convex is wired for client-side studio components.
• Vitest, Convex testing, Sharp-compatible Node tests, and Playwright are configured.
• The root page links into the studio entry point.
• README development setup is updated enough for another contributor to run the app.

Acceptance criteria

• Root page renders without product features implemented.
• Studio route is reachable from the root page.
• Convex provider is available to client components.
• Test harnesses can run at least one smoke test in each configured layer.
• No local secrets or generated .env files are committed.

Blockers

None.

What can make this fail

• Scaffolding creates a nested app structure that complicates Vercel deployment.
• Convex setup requires local secrets that accidentally leak into git.
• Test tools are installed but not actually runnable in the same project shape.
• Sharp-compatible testing is skipped, creating later surprises when SVG export work starts.

How should Codex verify it

• Run the project’s install/build/lint/test commands once they exist.
• Run the initial Vitest suite.
• Run the initial Convex test/smoke path.
• Run Playwright against the root page and studio route.
• Check git status for generated secrets or duplicate/empty files.