Support Playwright storageState or setup hook for pre-authenticated demos

[DeDuckProject]

Problem

Some apps require authentication before any page can be recorded — password-gated staging environments, login-required apps, etc. Currently there's no first-class way to pre-authenticate the Playwright browser context before the LLM-generated demo script runs.

Workarounds today:

• Pass a hint to the LLM describing how to log in (fragile — depends on the LLM generating correct auth code)
• Bake auth into a custom startCommand pre-script (complex, non-obvious)

Desired behaviour

A config option that lets users provide either:

Option A — storageState path: Load a saved Playwright browser storage state (cookies + localStorage) before running the demo. The user generates this file once (e.g. via a setup script or separately) and commits it or produces it in CI.

app: {
  storageState: '.auth/state.json', // loaded into every Playwright context
}

Option B — beforeDemo hook: A path to a TypeScript file exporting an async setup(page) function that runs before the generated demo script. The user can handle login, cookie injection, etc.

app: {
  beforeDemo: './scripts/glimpse-setup.ts',
}

Notes

• Option A is lower friction for simple cookie-based auth (e.g. Shopify dev store password gate)
• Option B is more flexible but requires more from the user
• Both could coexist — storageState for simple cases, beforeDemo for complex ones
• TBD: decide which option(s) to implement based on demand