feat: add live-cycling LSP completion

src/main.rs

@@ -30,7 +30,9 @@ Visual: motions extend selections, y copy, d/x/Delete cut, c change
         I/A insert at each selected line's first nonblank/end
         Ctrl+l split rows, Ctrl+n add occurrence, Ctrl+s skip, Ctrl+a all
         v/V switches selection shape; same selector or Esc cancels retaining carets
-Insert: Esc returns to Normal retaining carets
+Insert: Ctrl+n requests LSP completion at primary caret, then cycles next; Ctrl+j/k next/previous
+        Candidates replace text live; Original text restores it; other keys close and act normally
+        Enter inserts newline, Tab inserts tab, Esc returns to Normal retaining candidate/carets
 Search: Enter finds next literal match, Esc cancels (case-sensitive, wraps)
 Commands: :w [PATH], :q, :q!, :wq [PATH], :plugins, :PLUGIN [ARGS]
 Buffers: :edit PATH, :buffers, :buffer N, :bnext, :bprev, :bdelete[!] [N]