fix(tui): refresh scroll height at cached bottom

ui-tui/src/__tests__/scroll.test.ts

@@ -3,9 +3,12 @@ import { describe, expect, it, vi } from 'vitest'
 import { scrollWithSelectionBy } from '../app/scroll.js'
 
 function makeScroll(overrides: Partial<Record<string, unknown>> = {}) {
+  const getScrollHeight = (overrides.getScrollHeight as (() => number) | undefined) ?? vi.fn(() => 100)
+
   return {
+    getFreshScrollHeight: vi.fn(() => getScrollHeight()),
     getPendingDelta: vi.fn(() => 0),
-    getScrollHeight: vi.fn(() => 100),
+    getScrollHeight,
     getScrollTop: vi.fn(() => 10),
     getViewportHeight: vi.fn(() => 20),
     getViewportTop: vi.fn(() => 0),
@@ -34,6 +37,47 @@ describe('scrollWithSelectionBy', () => {
     expect(s.scrollBy).toHaveBeenCalledWith(1)
   })
 
+  it('uses fresh scroll height when cached height would swallow a down-scroll at a fake bottom', () => {
+    const s = makeScroll({
+      getFreshScrollHeight: vi.fn(() => 34),
+      getScrollHeight: vi.fn(() => 30),
+      getScrollTop: vi.fn(() => 10),
+      getViewportHeight: vi.fn(() => 20)
+    })
+
+    const selection = {
+      captureScrolledRows: vi.fn(),
+      getState: vi.fn(() => null),
+      shiftAnchor: vi.fn(),
+      shiftSelection: vi.fn()
+    }
+
+    scrollWithSelectionBy(10, { scrollRef: { current: s as never }, selection })
+
+    expect(s.scrollBy).toHaveBeenCalledWith(4)
+  })
+
+  it('uses fresh height when pending down-scroll reaches the cached fake bottom', () => {
+    const s = makeScroll({
+      getFreshScrollHeight: vi.fn(() => 38),
+      getPendingDelta: vi.fn(() => 2),
+      getScrollHeight: vi.fn(() => 32),
+      getScrollTop: vi.fn(() => 10),
+      getViewportHeight: vi.fn(() => 20)
+    })
+
+    const selection = {
+      captureScrolledRows: vi.fn(),
+      getState: vi.fn(() => null),
+      shiftAnchor: vi.fn(),
+      shiftSelection: vi.fn()
+    }
+
+    scrollWithSelectionBy(10, { scrollRef: { current: s as never }, selection })
+
+    expect(s.scrollBy).toHaveBeenCalledWith(6)
+  })
+
   it('does nothing at the edge instead of queueing dead pending deltas', () => {
     const s = makeScroll({
       getScrollHeight: vi.fn(() => 30),