A module's runtime waits for its broker credential and its account at a start, bounded, instead of exiting (issue 1496)

The node-engine starts a module's runtime before the provisioner's client fills
its broker file, and the bus carries a new account only after it reloads its
users. The runtime exited on both and was restarted until they were there (ace,
2026-10-26 21:19: mesh-build-node's and mesh-build-image's runtimes exited twice).
It now waits up to five minutes from its start, said once: the file is read again
each time its directory changes (the bundles' inotify watch, a 30 s backstop),
and an authorization refusal is asked again with the backoff. Past the bound it
gives up loudly; a file with no url, a pin mismatch and a bad URL stay final.

node-tools/internal/runtime/watch.go

@@ -37,6 +37,14 @@ type bundleWatch struct {
 	done    chan struct{}
 }
 
+// WatchFile hears, as the bundles are heard, the directory of the file at path, or the nearest directory above it that
+// exists, and calls changed once at its start and once after each burst of changes there has settled: a runtime waiting
+// for its broker credential reads it again when the node-engine writes it, never on a clock (issue 1496). It answers its
+// stop.
+func WatchFile(path string, changed func(), logf func(string, ...any)) (func(), error) {
+	return watchBundles([]string{path}, changed, logf)
+}
+
 // watchBundles starts the watch of the entrypoints at paths. It answers its stop.
 func watchBundles(paths []string, changed func(), logf func(string, ...any)) (func(), error) {
 	fd, err := unix.InotifyInit1(unix.IN_CLOEXEC | unix.IN_NONBLOCK)