GeezerVison

Follow-up to #633. A rewrite cached with cooldown on expired after a fixed time (an hour, less with short cooldowns), so with a 3d cooldown every packument was rewritten again each hour, for pnpm 12 the whole lockfile.

A cached rewrite only goes wrong when a version it held back leaves cooldown: versions it let through stay allowed, and a new upstream version changes the document and so the cache key. So it now expires then.

• Handlers ask cooldown through Proxy.cooldown(), which reports the availability time (Decision.AvailableAt) of each version it holds back to the rewrites running at that moment. A rewrite expires at the earliest one.
• A rewrite can hear of a version another rewrite held back at the same time. That only makes it expire earlier, never later, and keeps the ecosystems' filters as they are.
• A rewrite that held nothing back, or held back a version without a known time, is kept for the shortest cooldown configured, at least a minute and at most a day.
• A test fails when a handler asks Proxy.Cooldown directly, since that decision would not reach the rewrites.

Tested through the npm and Composer handlers: a version published 2h ago with a 3h cooldown gives an entry that expires an hour later.