Addresses Copilot review on PR #392.
Both tasks inside `postUpsertTasks` already swallow their rejections via
`.catch`, so `Promise.all([taskA.catch, taskB.catch])` never rejects, and
`postUpsertMutex.mutex(... postUpsertTasks)` therefore never rejects in
practice. The outer `.catch` could only fire on AsyncMutex internal
corruption — an extremely rare event, and one whose log message would
be misleading ("background post-upsert work failed" pointing at the
mutex layer, not the work).
Replace with `void postUpsertWork`: marks the floating promise as
intentional, and lets a truly unexpected rejection surface as an
UnhandledPromiseRejection — a loud, attributable signal of a real bug
rather than a swallowed warn buried in logs.
Renato Alcara
b0c34cb536