Wrap toast bodies, slim the dismiss hint, and stop flicker

Toasts now render three content rows with word-wrapped bodies. The
in-toast "Ctrl-N · N more" hint is replaced by a short
"Ctrl-N · dismiss" entry on the status strip that only appears
while a notification is live.

The box stops flickering while the focused child repaints its TUI:
the overlay is stitched onto the per-chunk PTY write under outMu
and bracketed by DECSET 2026 so supporting terminals buffer the
child's redraw and the box paint into a single frame.

internal/app/toast_test.go

@@ -1,6 +1,9 @@
 package app
 
-import "testing"
+import (
+	"strings"
+	"testing"
+)
 
 func TestToastStackPushAndOrder(t *testing.T) {
 	var s toastStack
@@ -98,3 +101,64 @@ func TestToastStackSnapshotIsCopy(t *testing.T) {
 		t.Fatalf("snapshot is not an independent copy: %#v", again)
 	}
 }
+
+func TestWrapToastBodyFixedHeight(t *testing.T) {
+	got := wrapToastBody("short", 20)
+	if len(got) != toastContentRows {
+		t.Fatalf("len = %d, want %d", len(got), toastContentRows)
+	}
+	if got[0] != "short" {
+		t.Fatalf("line 0 = %q, want \"short\"", got[0])
+	}
+	if got[1] != "" || got[2] != "" {
+		t.Fatalf("trailing pads not empty: %#v", got)
+	}
+}
+
+func TestWrapToastBodyWrapsOnWordBoundary(t *testing.T) {
+	got := wrapToastBody("the quick brown fox jumps over", 10)
+	// Expect greedy fill: "the quick" (9), "brown fox" (9), "jumps over" (10).
+	want := []string{"the quick", "brown fox", "jumps over"}
+	for i, w := range want {
+		if got[i] != w {
+			t.Fatalf("line %d = %q, want %q (full=%#v)", i, got[i], w, got)
+		}
+	}
+}
+
+func TestWrapToastBodyEllipsizesOverflow(t *testing.T) {
+	got := wrapToastBody("alpha beta gamma delta epsilon zeta eta theta", 6)
+	if len(got) != toastContentRows {
+		t.Fatalf("len = %d, want %d", len(got), toastContentRows)
+	}
+	last := got[toastContentRows-1]
+	if !strings.HasSuffix(last, "…") {
+		t.Fatalf("overflow should ellipsize last line, got %q (full=%#v)", last, got)
+	}
+	if visibleLen(last) > 6 {
+		t.Fatalf("last line %q exceeds width 6", last)
+	}
+}
+
+func TestWrapToastBodyBreaksOverlongWord(t *testing.T) {
+	got := wrapToastBody("supercalifragilistic", 6)
+	if got[0] != "superc" {
+		t.Fatalf("line 0 = %q, want \"superc\"", got[0])
+	}
+	if got[1] != "alifra" {
+		t.Fatalf("line 1 = %q, want \"alifra\"", got[1])
+	}
+	// Third line should hold the rest (possibly ellipsized).
+	if got[2] == "" {
+		t.Fatalf("line 2 unexpectedly empty: %#v", got)
+	}
+}
+
+func TestWrapToastBodyEmptyInput(t *testing.T) {
+	got := wrapToastBody("", 20)
+	for i, l := range got {
+		if l != "" {
+			t.Fatalf("line %d = %q, want \"\"", i, l)
+		}
+	}
+}