"origin sync: incremental, event-shaped, and polite > a conditional request is answered from the cache, not refetched" passes every time on a loaded check machine #5201

Intent: origin sync: incremental, event-shaped, and polite > a conditional request is answered from the cache, not refetched in test/origins-sync.test.ts goes red in pulls that never touch it (pull #5122), so good work is parked and the board shows red noise.

Done:

• [ ] the pull names the cause (wall clock, a real sleep, a shared port or directory, a fake clock mixed with Date.now(), a budget measured end to end instead of in the code it guards)
• [ ] bun test --rerun-each 30 test/origins-sync.test.ts passes, and also passes with other test files running beside it (bun test test/origins-sync.test.ts test/apps.test.ts). The pull says how it was checked
• [ ] the test still fails when the behaviour it guards is broken; what it promises about the product is unchanged. A time or resource budget may only move to what the code itself spends, never just get wider

Files: test/origins-sync.test.ts; the source only if the flake is a real race there (then the pull says so). Hint: the fake origin's request counter and the sync's cache can race with a background tick; drive one sync and count after it resolves.