feat: add Visual selection and clipboard editing

src/main.rs

@@ -11,6 +11,8 @@ Normal: i/a insert, I/A insert at first nonblank/end, o/O new line
         h/j/k/l move, 0/$ line ends, x delete, J join lines
         w/b/e word next/previous/end, W/B/E whitespace-delimited WORDs
         u undo, U redo, : command, / search, n/N next/previous match
+        v select, p/P paste after/before cursor
+Visual: motions extend selection, y copy, d/x/Delete cut, v/Esc cancel
 Insert: Esc returns to normal
 Search: Enter finds next literal match, Esc cancels (case-sensitive, wraps)
 Commands: :w [PATH], :q, :q!, :wq [PATH], :plugins, :PLUGIN [ARGS]