Fix error flashes replacing focused pane

internal/app/app.go

@@ -2268,8 +2268,17 @@ func (st *uiState) flashError(msg string) {
 	st.mu.Lock()
 	st.attentionText = msg
 	st.attentionAt = "" // shows on every focus until cleared
+	focusedPad := st.focusedPad
+	focusedID := st.focusedID
 	st.mu.Unlock()
-	st.renderEmptyState()
+	switch {
+	case focusedPad != "":
+		st.repaintFocusedPad()
+	case focusedID != "":
+		st.repaintFocused()
+	default:
+		st.renderEmptyState()
+	}
 	st.drawTabBar()
 	st.drawSidebar()
 	st.drawStatusLine()

internal/harness/scenarios/error_flash_preserves_focused_pane.json

@@ -0,0 +1,37 @@
+{
+  "name": "error_flash_preserves_focused_pane",
+  "presets": {
+    "processes": [
+      {
+        "name": "steady",
+        "argv": ["sh", "-lc", "printf 'STEADY READY\\n'; sleep 5"]
+      }
+    ]
+  },
+  "trust": ["steady"],
+  "steps": [
+    {
+      "type": "mcp_call",
+      "method": "spawn_process",
+      "params": {"kind": "command", "preset": "steady", "name": "steady"},
+      "save_as": "proc"
+    },
+    { "type": "wait_text", "contains": "STEADY READY", "timeout_ms": 5000 },
+    { "type": "send_chord", "chord": "ctrl-k" },
+    { "type": "send_text", "text": "Open Settings" },
+    { "type": "send_chord", "chord": "enter" },
+    { "type": "send_chord", "chord": "enter" },
+    { "type": "send_chord", "chord": "ctrl-n" },
+    { "type": "send_chord", "chord": "ctrl-n" },
+    { "type": "send_chord", "chord": "ctrl-n" },
+    { "type": "send_chord", "chord": "ctrl-n" },
+    { "type": "send_chord", "chord": "ctrl-n" },
+    { "type": "send_chord", "chord": "ctrl-n" },
+    { "type": "send_chord", "chord": "ctrl-n" },
+    { "type": "send_chord", "chord": "enter" },
+    { "type": "wait_text", "contains": "no active top-level agent to summarize", "timeout_ms": 5000 },
+    { "type": "wait_text", "contains": "STEADY READY", "timeout_ms": 5000 },
+    { "type": "assert_contains", "contains": "STEADY READY" },
+    { "type": "assert_not_contains", "contains": "Press Ctrl-K to spawn an agent or process" }
+  ]
+}