Upgrade to 1.0.0-rc880

Concerns: pushword/static-generator

lastGeneratedAt is re-read at each request

Only under a long-running worker (FrankenPHP, Symfony Runtime). The generation state was read once per worker process and kept, so GET /api/static/{host} could answer completed carrying the lastGeneratedAt of the previous generation until that worker recycled.

Affected: any client polling that endpoint to decide a generation is done. Nothing to do — a client that worked around it, by ignoring the timestamp or waiting for it to move, can stop.