Review round three, credentials half. dsh-atomic-write grows the
cross-process writer-lock primitive (withFileLock: wx sentinel, bounded
backoff, stale takeover via onStaleBreak, deadline failure) plus a dirMode
option, and settings-local migrates its private copy to it; both providers
now create harness-home directories 0700.
credentials-local reuses the reviewed settings-local shape: watcher
reloads and line edits share one settled operation chain; every write
re-reads the document under the lock and publishes unobserved external
entries before editing, so an edit inside the debounce window (or another
process's write) can never be overwritten; the watcher's ready signal
queues one reconcile closing the startup gap.
The line editor is now physical-line aware: continuation lines of a
quoted multi-line value are never mistaken for assignments, untouched
lines keep their exact bytes (CRLF included), an edited line keeps its
own terminator, and appends use the document's dominant ending. A
multi-line entry reports writable: false, matching what set() would do.
The Credentials base class owns a contained notifyUpdated fan-out:
providers publish only after the commit, every listener runs, sync throws
and async rejections are logged without failing the committed write, and
INVARIANT-coded failures rethrow after the fan-out.
Yichen Jiang