feat: make senders tappable and replace the toasts with a fixed status line

src/app.rs

@@ -525,14 +525,14 @@ impl Carrier {
                 self.stash_draft();
                 self.selected_own = false;
                 self.selected_contact = Some(address);
-                self.open = None;
+                // The open message stays: the detail shows over it while
+                // its list highlight holds, and picking it again returns.
                 self.page = Page::Mail;
             }
             Message::OwnSelected => {
                 self.stash_draft();
                 self.selected_own = true;
                 self.selected_contact = None;
-                self.open = None;
                 self.page = Page::Mail;
             }
             Message::FetchCancelled => {
@@ -1029,13 +1029,30 @@ mod tests {
         assert_eq!(app.busy.as_deref(), Some("fetching"));
     }
 
+    fn opened() -> OpenedMsg {
+        OpenedMsg {
+            id: "ab".repeat(32),
+            from: String::new(),
+            subject: String::new(),
+            time: 0,
+            body: String::new(),
+            sender: String::new(),
+            reply_to: None,
+            kept: false,
+        }
+    }
+
+    #[test]
     #[test]
     fn contact_selection_and_message_selection_supersede_each_other() {
         let mut app = app();
+        // An open message survives a contact selection: the detail pane
+        // shows the contact while the mail keeps its list highlight.
+        app.open = Some((Folder::Inbox, opened()));
         app.handle(Message::ContactSelected("bob@localhost".into()));
         assert_eq!(app.selected_contact.as_deref(), Some("bob@localhost"));
         assert_eq!(app.page, Page::Mail);
-        assert!(app.open.is_none());
+        assert!(app.open.is_some());
 
         // busy does not block selecting a contact
         app.busy = Some("fetching".into());
@@ -1046,10 +1063,11 @@ mod tests {
     #[test]
     fn own_and_contact_selection_supersede_each_other() {
         let mut app = app();
+        app.open = Some((Folder::Inbox, opened()));
         app.handle(Message::OwnSelected);
         assert!(app.selected_own);
         assert_eq!(app.page, Page::Mail);
-        assert!(app.open.is_none());
+        assert!(app.open.is_some());
 
         app.handle(Message::ContactSelected("bob@localhost".into()));
         assert!(!app.selected_own);