Add scrollback text selection/copy, route all /whois output to wIRC main, bump to 0.1.8

- Scrollback (channel windows and wIRC main): mouse drag selection, double-click word,
  triple-click line, shift-click extend, Ctrl+C / Ctrl+Insert, Ctrl+A, Esc, and a
  right-click menu (Copy / Copy line / Select all). Copies one line per message.
  Clipboard writes go off the UI thread with a timeout, like the paste handler.
  Auto-scroll pauses while selecting and catches up once the selection is cleared.
- /whois: header, every reply line, related numerics (401/402/716/263...) and server or
  services notices arriving right after it all go to wIRC main under a bold
  "===== WHOIS <nick> (<server>) =====" header, counted by its unread indicator.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main/kotlin/ui/MainScreen.kt

@@ -168,8 +168,9 @@ fun MainScreen(
             }
         }
         Spacer(Modifier.height(4.dp))
-        // MOTD, numerics, errors, services/server notices and WHOIS replies whose window
-        // is gone - see ConnectionManager. Same rendering and auto-scroll as a channel window.
+        // MOTD, numerics, errors, services/server notices and all /whois output - see
+        // ConnectionManager. Same rendering, auto-scroll and text selection as a channel
+        // window.
         MessageScrollback(
             messages = mainMessages,
             displaySettings = displaySettings,