tests/eject/persist-written: count the worker's own snapshot of a visit

The persist worker snapshots about a second after a save (k_fs_saves).
When the probe's exit reaches the page later than that (a loaded host),
that snapshot stores the probe's file and the page's last one has nothing
left to store: "stored 0 file(s)" for a visit that wrote one. The page now
reports what every snapshot of the visit stored (app.js state
persistedWrote), the worker's own included. With the last snapshot held
back 3 s, the old check fails visits 1 and 2 as the loaded gate did; this
one passes.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_c8c04c00da9a4525ab21b0b9f146c598

tests/eject/persist-written.html

@@ -5,7 +5,8 @@
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <title>persist-written</title>
 <!-- tests/eject/persist-written.sh: /save kept in IndexedDB; ?visit=N is the
-     probe's argument. After the probe exits the page takes a snapshot. -->
+     probe's argument. After the probe exits the page takes a snapshot; the
+     status names what every snapshot of the visit stored. -->
 <style>html, body { margin: 0; background: #0b0b0d; color: #ddd; font: 14px/1.4 system-ui, sans-serif; }</style>
 </head>
 <body>
@@ -36,6 +37,9 @@ try {
   st.textContent = 'running';
   const code = await app.exited;
   const r = await globalThis.__ntPersist?.();
+  // What the visit stored: the worker's own snapshot soon after the probe's
+  // save may already have stored it, leaving this last one nothing to do.
+  if (r) r.wrote = app.state.persistedWrote ?? r.wrote;
   st.textContent = `exited (${code}) synced ${JSON.stringify(r)}`;
 } catch (e) {
   st.textContent = 'failed: ' + (e?.message ?? e);

web/src/app.js

@@ -697,7 +697,9 @@ async function begin(opts, base, at, state, meter) {
   if (keep) {
     const p = persist(keep.db, keep.dir, await globalKernel(), {
       every: Number(sw.persistms || 30000),
-      onSync: (m) => { state.persisted = m; },
+      // `persistedWrote`: the files every snapshot of this visit stored,
+      // the ones it took of its own after a save included.
+      onSync: (m) => { state.persisted = m; state.persistedWrote = (state.persistedWrote ?? 0) + (m.wrote ?? 0); },
     });
     globalThis.__ntPersist = () => p?.sync();
   }