An action on a name that is no app answers 404, not 'settings cannot be saved' (found walking capability map B2 on 9202)

Test TestAnActionOnANameThatIsNoAppIsA404 red first. Commit only.

CHANGELOG.md

@@ -40,6 +40,11 @@ night report (`audits/night-2026-10-28/`).
   and said once; no agent (9202) = Docker's flag only, as before. The inspect now reads `{{.Id}}` too. Tests
   `TestR528_*` (stacks, cmd/controller), red before the fix (the host-counted kill was not seen) or red-proved by
   mutation (the back-off, the wiring).
+- **Found walking the capability map's B2 on 9202 (small, fixed in the session):** a Stop/Start of a name that is no
+  app on the box (the bootstrap-managed `felhom-controller`) answered 500 „…az alkalmazás beállításai nem menthetők." —
+  the desired-state write's „not found" read as a save failure. `stacks.SetDesiredState` returns the
+  `ErrStackNotFound` kind with the household's sentence (`err.stacks.alkalmazas_nem_talalhato`); `actionStack` answers
+  404 before recording any intent. Nothing was ever stopped. Test `TestAnActionOnANameThatIsNoAppIsA404` (red first).
 - **H8 — `internal/backup/restore_copy_sweep.go`:** an unused restore copy goes after 14 days. Every 6 hours
   (`restore-copy-sweep`) a copy is removed only when the app has no restore hold of any kind, the app-stop marker is
   readable and does not name the app, no restore runs, and the copy is older than 14 days. Tests `TestR1256_H8_*`