fix(tui): trim whitespace-only selection chrome

- clamp selection highlight to real row content so blank drag margins do not render or copy
- keep successful copy actions quiet while preserving usage and failure feedback

ui-tui/src/app/slash/commands/core.ts

@@ -269,7 +269,6 @@ export const coreCommands: SlashCommand[] = [
       }
 
       writeOsc52Clipboard(target.text)
-      sys(`copied ${target.text.length} chars`)
     }
   },