Add a test for dragging a range selection past the bottom of a panel

This is the other place that manages its own scroll position: while a
drag extends the selection to a line below the viewport, the view stays
put, and the drag autoscroller scrolls it one line at a time for as long
as the pointer stays there. Making the scroll automatic would centre the
selection instead, i.e. jump the view rather than scroll it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/integration/tests/test_list.go

@@ -500,6 +500,7 @@ var tests = []*components.IntegrationTest{
 	ui.BranchesNotFirstTab,
 	ui.CommitsNotFirstTab,
 	ui.DisableSwitchTabWithPanelJumpKeys,
+	ui.DragBeyondViewport,
 	ui.EmptyMenu,
 	ui.HideSidePanel,
 	ui.KeybindingSuggestionsDontCrashOnDisabledBindings,

pkg/integration/tests/ui/drag_beyond_viewport.go

@@ -0,0 +1,37 @@
+package ui
+
+import (
+	"fmt"
+
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var DragBeyondViewport = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Dragging a range selection beyond the bottom of the panel doesn't scroll the view",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	Width:        120,
+	Height:       30,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("initial commit")
+		for i := range 20 {
+			shell.CreateFile(fmt.Sprintf("file%02d", i), "")
+		}
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			Focus().
+			OriginY(0).
+			// The pointer ends up below the panel, so the range extends to a line
+			// that isn't visible. Scrolling there is the drag autoscroller's job,
+			// which scrolls line by line for as long as the pointer stays there;
+			// the drag itself must leave the scroll position alone.
+			ClickAndHold(1, 1).
+			MouseMove(1, 8).
+			MouseRelease().
+			SelectedLineIdx(8).
+			OriginY(0)
+	},
+})