One background thread for blocking write jobs, for the settings.json /
wallets.json saves and the tx-history snapshot that later commits move
off the UI thread. Jobs are keyed (a file path, "tx-history"):
- a submit for a key that is still queued replaces that job and keeps
its place in line (latest wins);
- keys run first in, first out, one job at a time, so two writes of one
file never overlap and an older snapshot never lands after a newer one;
- submitAndWait() blocks until that job (or a newer one for the key) has
run and returns its result, for writes the caller needs on disk;
- flush() waits with a bound; stop() runs everything queued, then joins;
- the thread starts on first use and sleeps when idle; with no thread
(none could be created, or after stop()) a job runs inline.
persistFileAtomically() routes Platform::writeFileAtomically through a
writer, or writes synchronously when there is none. Nothing uses it yet.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
