Regression-protection test: init() propagates the loader rejection
before pdfjsReady is set, so the renderer stays in a safe unready state.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Adds an optional LibLoader parameter (defaults to the real pdfjs-dist dynamic
imports) and a failing test that verified the loader is called during init().
This is the first step toward removing ManualMockedModule registrations that
race with vitest-browser-playwright's birpc teardown (#535).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>