fix(stalker): serialize overlapping edits

docs/architecture/stalker-portal.md

@@ -199,11 +199,13 @@ device IDs and signatures as one connection identity. A metadata-only edit
 does not run discovery and preserves the stored connection byte-for-byte.
 Changing any connection field disables the form while the same discovery
 service validates the draft. Auth rejection or an unreachable portal leaves
-the dialog open and writes nothing. Before discovery starts, Edit reserves the
-playlist ID, blocks every new authentication (including a URL edit with the same
-normalized fingerprint) and repair, and drains any work already in flight.
-Ownership is rechecked after every asynchronous drain or authority rebase;
-failure releases that reservation with the previous runtime untouched.
+the dialog open and writes nothing. Escape/backdrop closure is disabled for the
+validation window. Before discovery starts, Edit reserves the playlist ID; an
+overlapping Edit cannot replace that owner. The reservation blocks every new
+authentication (including a URL edit with the same normalized fingerprint) and
+repair, and drains any work already in flight. Ownership is rechecked after
+every asynchronous drain or authority rebase; failure releases that reservation
+with the previous runtime untouched.
 Success atomically replaces the endpoint, mode and normalized identity together
 with session metadata: simple mode
 clears token/fingerprint/watchdog/account state, while full mode replaces it