disallow to disable guard during focus

README.md

@@ -77,6 +77,10 @@ agent enforces them on your machine:
   `*discord*`, matched against the process name and its command line.
 * **When** — only while a focus interval runs (the default), always, or on a
   schedule. Breaks can keep the block on or let it go.
+* **One-way while you work** — the guard can be switched on whenever you like, but
+  not off while an interval is live, breaks and pauses included; the desktop app's
+  local enforcement switches lock the same way. Finishing or dropping the interval
+  frees it. A guard you can disable the moment it starts to bite is decoration.
 * Every attempt that gets turned away is recorded — and teased about in the
   evening report.