fix(custom-cli): retrait de l'overlay busy plein panneau — blocage du chat seul — #247 (QA verte)

Les cellules custom CLI ne rendent plus le TargetAnnouncementsOverlay quand
l'agent est busy : le badge busy canonique et le lock du composer (comportement
du chat après envoi d'un message) suffisent, la vue terminal/chat reste visible.
Les cellules TUI natives conservent le voile plein panneau.

frontend/src/features/layout/LayoutGrid.tsx

@@ -1561,11 +1561,10 @@ function LeafView({
           </div>
         )}
         {/* F3 (ticket #4): while another agent is talking to THIS agent (target),
-            an availability veil showing its live réflexions. Driven by the target's
-            busy state (agentBusyChanged + read-model hydration), never by the raw
-            PTY — it retracts at idle even when a turn ends without a completion
-            event. Self-guards on `active` (busy) and renders null otherwise. */}
-        {!modelServerOverlay && agentId != null && (
+            an availability veil showing its live réflexions. Native TUI cells
+            need the full-cell guard; custom CLI cells keep the canonical busy
+            badge and composer lock only, matching their normal chat turn flow. */}
+        {!modelServerOverlay && cellMode !== "custom" && agentId != null && (
           <TargetAnnouncementsOverlay
             projectId={projectId}
             agentId={agentId}