[E-OWL-1] Core Owlbear extension scaffold and marketplace submission

[alxjrvs]

Part of #945

Phase 1: Core Owlbear extension scaffold and marketplace submission

Updated 2026-03-24: The codebase has @randsum/dice-ui (in packages/dice-ui), not @randsum/component-library. Use @randsum/dice-ui components or purpose-built components.

Scope

A working Owlbear Rodeo extension that renders a dice roller panel inside an iframe. Users can type notation, roll, and see results with modifier breakdown. Submit to the Owlbear marketplace as soon as functional.

Acceptance Criteria

• apps/owlbear workspace package scaffolded with Vite + @vitejs/plugin-react — private, deploys as a static site
• Extension metadata correct: name "randsum Dice", icon, category "Dice"
• OBR.onReady() initializes the extension; iframe loads from the hosted HTTPS origin
• Notation input renders inside the extension panel, validates using isDiceNotation
• Roll button executes roll() and displays results with modifier breakdown
• UI is functional and usable at 320px width
• HTTPS hosting configured with frame-ancestors CSP header allowing Owlbear to embed the iframe
• Extension submitted to the Owlbear marketplace
• @owlbear-rodeo/sdk pinned to a major version in package.json

Implementation Notes

• The iframe is a standard React webpage — standard Vite + React bundling
• Local dev requires HTTPS: use vite --https with a self-signed cert or ngrok/Cloudflare Tunnel
• Submit to marketplace as soon as Phase 1 is functional — don't wait for roll history
• CSP: add Content-Security-Policy: frame-ancestors https://*.owlbear.rodeo to hosting config

Out of Scope

• Roll history panel (Phase 2, [E-OWL-2] Roll history panel #974)
• Game system selector
• Shared roll log visible to other players
• Owlbear room state API integration