[oliverandrich]

Playwright 1.63 added context.credentials, a virtual WebAuthn authenticator per browser context.
playwright_ex already carries these credentials in the storage state, but has no wrapper for the API itself.

This adds four functions to PlaywrightEx.BrowserContext, one per protocol method:

• credentials_install/2 installs the authenticator into the context.
• credentials_create/3 seeds a credential for a relying party, generated or imported.
• credentials_get/2 lists the credentials, optionally filtered by :id or :rp_id.
• credentials_delete/3 removes a credential by id.

They follow the existing channel functions: NimbleOptions schemas, typespecs and links to the Playwright docs.
Returned credentials have the same shape as those in storage_state/2.

Why

I maintain Ithibati, a passkey library for Phoenix.
Its browser tests add a virtual authenticator over a raw CDP session today.
With these wrappers they can use Playwright's own authenticator instead.

Tests

Five tests in browser_context_test.exs:

• seeding, filtering and deleting a credential
• importing a known credential
• a page registering a passkey after credentials_install/2
• a seeded credential answering navigator.credentials.get(), with the sign count incremented
• a page without credentials_install/2 keeping the browser's own WebAuthn

mix check passes.