feat(gui): focus the viewer code field when the View screen opens

Entering View now grabs keyboard focus on the code field (once, via a
one-shot flag so it doesn't steal focus every frame), so the user can paste
or type the share code immediately without clicking into it first.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/gui/mod.rs

@@ -211,6 +211,9 @@ struct ViewerState {
     /// Short endpoint id we're dialing, decoded from the ticket at Connect.
     /// Shown in the "Connecting to …" line so a dead host is identifiable.
     connecting_to: Option<String>,
+    /// Set when the View screen opens so the code field grabs focus once
+    /// (cleared on use, so it doesn't steal focus every frame).
+    focus_ticket: bool,
     error: Option<String>,
 }
 
@@ -613,6 +616,11 @@ impl PixelPassApp {
                 )
             })
             .inner;
+        // Grab focus once on screen entry so the user can paste/type straight
+        // away without first clicking into the field.
+        if std::mem::take(&mut self.viewer.focus_ticket) {
+            ticket_resp.request_focus();
+        }
         // Enter in the field connects (gated on a decodable code below).
         let enter_pressed =
             ticket_resp.lost_focus() && ui.input(|i| i.key_pressed(egui::Key::Enter));
@@ -702,6 +710,7 @@ impl PixelPassApp {
         {
             self.viewer.ticket_input = text.trim().to_string();
         }
+        self.viewer.focus_ticket = true;
     }
 
     fn start_viewer(&mut self, ctx: egui::Context) {