feat: add multiple buffers and file switching

src/main.rs

@@ -22,6 +22,8 @@ Visual: motions extend selections, y copy, d/x/Delete cut, c change
 Insert: Esc returns to Normal retaining 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]
+         :q refuses any dirty buffer; :wq saves active and quits only if all are clean
 
 Ruby config: $XDG_CONFIG_HOME/vamp/config.rb or ~/.config/vamp/config.rb
 Set VAMP_RUBY to choose the Ruby executable.";