irc: expand Send dialog input without allowing newlines

- Remove allow_newline; Enter triggers Send via is_enter_default.
- Keep use_available_height + condensed to reduce scroll bars.

Signed-off-by: Slendi <slendi@socopon.com>

main.lua

@@ -457,7 +457,7 @@ function IrcChatView:promptSendMessage()
     dialog = InputDialog:new{
         title = _("Send message"),
         input = "",
-        allow_newline = true,           -- allow multiline input
+        -- Keep single-line input semantics on Enter, but expand the box
         use_available_height = true,    -- expand input to available height
         condensed = true,               -- reduce extra padding to maximize text area
         buttons = {
@@ -465,6 +465,7 @@ function IrcChatView:promptSendMessage()
                 {
                     text = _("Send"),
                     is_default = true,
+                    is_enter_default = true,
                     callback = function()
                         local txt = dialog:getInputText()
                         -- Update buffer/UI before closing dialog to ensure immediate repaint