fix: PrevItem does not scroll viewport at top boundary

internal/tui/components/listviewport/listviewport.go

@@ -102,7 +102,7 @@ func (m *Model) NextItem() int {
 }
 
 func (m *Model) PrevItem() int {
-	atTopOfViewport := m.currId < m.topBoundId
+	atTopOfViewport := m.currId > 0 && m.currId <= m.topBoundId
 	if atTopOfViewport {
 		m.topBoundId -= 1
 		m.bottomBoundId -= 1

internal/tui/components/listviewport/listviewport_test.go

@@ -0,0 +1,119 @@
+package listviewport
+
+import (
+	"testing"
+	"time"
+
+	"github.com/dlvhdr/gh-dash/v4/internal/tui/constants"
+	"github.com/dlvhdr/gh-dash/v4/internal/tui/context"
+)
+
+func newTestModel(numItems, viewportHeight, itemHeight int) Model {
+	ctx := context.ProgramContext{}
+	dims := constants.Dimensions{Width: 80, Height: viewportHeight}
+	now := time.Now()
+	return NewModel(ctx, dims, now, now, "items", numItems, itemHeight)
+}
+
+func TestPrevItemScrollsAtTopBound(t *testing.T) {
+	// 10 items, viewport height 5, item height 1 => 5 items per page
+	// Initial bounds: topBoundId=0, bottomBoundId=4
+	m := newTestModel(10, 5, 1)
+
+	// Navigate down past the first page boundary
+	// After 5 NextItem calls: currId=5, topBoundId=1, bottomBoundId=5
+	for i := 0; i < 5; i++ {
+		m.NextItem()
+	}
+
+	if m.GetCurrItem() != 5 {
+		t.Fatalf("expected currId=5 after 5 NextItem calls, got %d", m.GetCurrItem())
+	}
+	if m.topBoundId != 1 {
+		t.Fatalf("expected topBoundId=1, got %d", m.topBoundId)
+	}
+
+	// Navigate back up to the top bound
+	// 4 PrevItem calls: currId goes 4, 3, 2, 1
+	for i := 0; i < 4; i++ {
+		m.PrevItem()
+	}
+
+	if m.GetCurrItem() != 1 {
+		t.Fatalf("expected currId=1, got %d", m.GetCurrItem())
+	}
+	if m.topBoundId != 1 {
+		t.Fatalf("expected topBoundId=1 (no scroll yet), got %d", m.topBoundId)
+	}
+
+	// Now one more PrevItem: currId should go to 0, and the viewport
+	// should scroll up so that item 0 is visible.
+	// Before fix: topBoundId stays at 1, item 0 is above the viewport.
+	// After fix: topBoundId becomes 0, item 0 is at the top of the viewport.
+	m.PrevItem()
+
+	if m.GetCurrItem() != 0 {
+		t.Fatalf("expected currId=0, got %d", m.GetCurrItem())
+	}
+	if m.topBoundId != 0 {
+		t.Errorf("PrevItem did not scroll up at the top boundary: expected topBoundId=0, got %d (item 0 is above the visible viewport)", m.topBoundId)
+	}
+}
+
+func TestNextItemScrollsAtBottomBound(t *testing.T) {
+	// Verify NextItem scrolling works symmetrically (this should pass already)
+	m := newTestModel(10, 5, 1)
+
+	// Navigate down to bottomBoundId (4)
+	for i := 0; i < 4; i++ {
+		m.NextItem()
+	}
+
+	if m.GetCurrItem() != 4 {
+		t.Fatalf("expected currId=4, got %d", m.GetCurrItem())
+	}
+	if m.topBoundId != 0 {
+		t.Fatalf("expected topBoundId=0 (no scroll yet), got %d", m.topBoundId)
+	}
+
+	// One more NextItem at the bottom boundary should scroll
+	m.NextItem()
+
+	if m.GetCurrItem() != 5 {
+		t.Fatalf("expected currId=5, got %d", m.GetCurrItem())
+	}
+	if m.topBoundId != 1 {
+		t.Errorf("NextItem did not scroll down at the bottom boundary: expected topBoundId=1, got %d", m.topBoundId)
+	}
+}
+
+func TestPrevItemAtFirstItem(t *testing.T) {
+	// Pressing up when already at the first item should stay at 0
+	// and should not corrupt viewport bounds.
+	m := newTestModel(10, 5, 1)
+
+	m.PrevItem()
+
+	if m.GetCurrItem() != 0 {
+		t.Errorf("expected currId=0, got %d", m.GetCurrItem())
+	}
+	if m.topBoundId != 0 {
+		t.Errorf("expected topBoundId=0 (should not scroll), got %d", m.topBoundId)
+	}
+	if m.bottomBoundId != 4 {
+		t.Errorf("expected bottomBoundId=4 (should not scroll), got %d", m.bottomBoundId)
+	}
+}
+
+func TestNextItemAtLastItem(t *testing.T) {
+	// Pressing down when already at the last item should stay at last
+	m := newTestModel(10, 5, 1)
+
+	for i := 0; i < 20; i++ {
+		m.NextItem()
+	}
+
+	if m.GetCurrItem() != 9 {
+		t.Errorf("expected currId=9, got %d", m.GetCurrItem())
+	}
+}