fix(tui): address copilot follow-up review on PR #16732 (#16740)

- moveCursor(extend=true) now collapses to the bare cursor when the
  computed offset equals the existing anchor instead of leaving a
  zero-length sel. Without this, Shift+Left at col 0 / Shift+Home at
  start would silently hide the hardware cursor (selected truthy)
  without rendering any highlight.
- _tui_need_npm_install also catches UnicodeDecodeError so a corrupted
  / non-UTF8 lockfile falls back to the mtime path the docstring
  promises instead of crashing.

Made-with: Cursor

ui-tui/src/components/textInput.tsx

@@ -638,14 +638,14 @@ export function TextInput({
 
   const moveCursor = (next: number, extend = false) => {
     const c = snapPos(vRef.current, next)
+    const anchor = selRef.current?.start ?? curRef.current
 
-    if (extend) {
-      const anchor = selRef.current?.start ?? curRef.current
+    if (!extend || anchor === c) {
+      clearSel()
+    } else {
       const nextSel = { end: c, start: anchor }
       selRef.current = nextSel
       setSel(nextSel)
-    } else {
-      clearSel()
     }
 
     setCur(c)