docs(path-b): cron entries for autosave + idle-sweep

Adds vibn-dev/CRON.md with copy-pasteable /etc/cron.d/vibn-path-b
template and smoke commands. Pairs with the
/api/admin/path-b/{autosave,idle-sweep} endpoints already shipped
in vibn-frontend.

Made-with: Cursor

vibn-dev/CRON.md

@@ -0,0 +1,105 @@
+# Path B cron entries
+
+Two background jobs keep dev containers cheap and recoverable. Wire
+both to whatever scheduler is convenient (host crontab, Coolify
+Scheduled Tasks, or a separate vibn-cron service later).
+
+## 1. Workspace autosave — every 5 min
+
+Force-pushes `/workspace` of every running dev container to a
+`vibn-autosave/main` branch in the project's Gitea repo. Throttled
+internally so it's safe to call more often than 5 min if needed.
+
+```cron
+*/5 * * * * curl -fsS -X POST \
+  -H "Authorization: Bearer $NEXTAUTH_SECRET" \
+  -H "Content-Type: application/json" \
+  -d '{"sweep":true}' \
+  https://vibnai.com/api/admin/path-b/autosave \
+  >> /var/log/vibn-autosave.log 2>&1
+```
+
+What it does on a per-project basis (see
+`autosaveWorkspace` in `vibn-frontend/lib/dev-container.ts`):
+
+1. Skips containers that aren't `state='running'`.
+2. Skips containers without a `.git` directory in `/workspace`.
+3. `git checkout -B vibn-autosave/main`, adds everything, commits if
+   there are changes, force-pushes.
+4. Records the push in `fs_dev_autosaves` (per-project history,
+   bounded by retention you can prune later).
+
+## 2. Idle-suspend sweep — every 5 min
+
+Suspends every running dev container whose last `shell.exec` is older
+than 30 minutes. Coolify-stops the service; the workspace + cache
+volumes persist; resume happens automatically on the next
+`shell.exec` (~3-5s).
+
+```cron
+*/5 * * * * curl -fsS -X POST \
+  -H "Authorization: Bearer $NEXTAUTH_SECRET" \
+  "https://vibnai.com/api/admin/path-b/idle-sweep?minutes=30" \
+  >> /var/log/vibn-idle.log 2>&1
+```
+
+Override the threshold per-tier later by passing a different
+`?minutes=` value. 30 was chosen because it covers a coffee break
+without disrupting active work.
+
+## Quick install on the Coolify host
+
+```bash
+sudo tee /etc/cron.d/vibn-path-b > /dev/null <<EOF
+NEXTAUTH_SECRET=<paste-from-.env.local-on-coolify>
+
+# Workspace autosave to Gitea
+*/5 * * * * root curl -fsS -X POST \
+  -H "Authorization: Bearer \$NEXTAUTH_SECRET" \
+  -H "Content-Type: application/json" \
+  -d '{"sweep":true}' \
+  https://vibnai.com/api/admin/path-b/autosave \
+  >> /var/log/vibn-autosave.log 2>&1
+
+# Idle-suspend dev containers (30m threshold)
+*/5 * * * * root curl -fsS -X POST \
+  -H "Authorization: Bearer \$NEXTAUTH_SECRET" \
+  "https://vibnai.com/api/admin/path-b/idle-sweep?minutes=30" \
+  >> /var/log/vibn-idle.log 2>&1
+EOF
+sudo chmod 0644 /etc/cron.d/vibn-path-b
+sudo systemctl reload cron
+```
+
+## Manual smoke
+
+```bash
+# autosave one project
+curl -X POST -H "Authorization: Bearer $NEXTAUTH_SECRET" \
+  -H "Content-Type: application/json" \
+  -d '{"projectId":"<vibn-project-id>"}' \
+  https://vibnai.com/api/admin/path-b/autosave
+
+# sweep all
+curl -X POST -H "Authorization: Bearer $NEXTAUTH_SECRET" \
+  -H "Content-Type: application/json" \
+  -d '{"sweep":true}' \
+  https://vibnai.com/api/admin/path-b/autosave
+
+# idle suspend (use a huge minutes value to dry-run safely)
+curl -X POST -H "Authorization: Bearer $NEXTAUTH_SECRET" \
+  "https://vibnai.com/api/admin/path-b/idle-sweep?minutes=99999"
+```
+
+## Disabling
+
+If something goes wrong, flip the kill switch — the chat will fall
+back to gitea-write tools and the cron sweeps will return `scanned: 0`
+because no containers will be running.
+
+```bash
+curl -X POST -H "Authorization: Bearer $NEXTAUTH_SECRET" \
+  https://vibnai.com/api/admin/path-b/disable
+```
+
+Re-enable later with `/api/admin/path-b/enable`.