fix(vidstack): pass emptied event to notify

[mihar-22]

Summary

• Accept the native emptied event in #onEmptied.
• Pass that event through to this.#ctx.notify("emptied", undefined, event).

Fixes #1778

Validation

• pnpm --filter vidstack typecheck passed.
• Initial typecheck attempt failed before dependency install because the new linked worktree had no node_modules and tsgo was not found; after pnpm install --frozen-lockfile, the requested command passed.