fix: gate idle recovery on exact runtime status

(cherry picked from commit 35597715018e598bf24f0b708cbd32b039533a99)

docs/rfcs/live-to-final-assistant-replies.md

@@ -476,9 +476,13 @@ Expected behavior:
   Missing, connecting, closed, or mismatched transports keep the normal stale
   state recovery path; a cached stream ID or busy flag is insufficient.
   OPEN is not proof that a terminal frame will arrive: an idle hint must also
-  schedule bounded canonical snapshot recovery without erasing the live scene.
-  A newer turn, replacement source, or received terminal event invalidates that
-  request; a still-active server snapshot is not permission to terminate work.
+  schedule bounded recovery without erasing the live scene. Before reading a
+  settled session snapshot, that recovery must check the exact stream's runtime
+  status. A runtime-active stream retains ownership even when persisted
+  `active_stream_id` and pending fields are already clear; only explicit
+  runtime inactivity permits canonical snapshot settlement. Probe failure is a
+  degraded/interrupted state, not evidence of successful completion. A newer
+  turn, replacement source, or received terminal event invalidates the request.
 - Background completion, cancellation, or failure should be represented without
   stealing the visible pane from the user.
 - Session switching should not erase pending live context, in-flight snapshots,