Fix Enter key semantics and add expandable model descriptions

- Replace TextEditor with NativeTextEditor (NSViewRepresentable) so plain
  Enter sends the message and Shift/Cmd+Enter inserts a newline. The old
  TextEditor passed bare Return directly to NSTextView before SwiftUI's
  onKeyPress could intercept it, accidentally making Cmd+Enter send instead.
- Add More…/Less toggle in ModelInfoView for descriptions longer than 250
  characters, with smooth expand/collapse animation.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

oAI/Views/Screens/ModelInfoView.swift

@@ -30,6 +30,7 @@ struct ModelInfoView: View {
 
     @Environment(\.dismiss) var dismiss
     @Bindable private var settings = SettingsService.shared
+    @State private var isDescriptionExpanded = false
 
     var body: some View {
         VStack(spacing: 0) {
@@ -78,8 +79,18 @@ struct ModelInfoView: View {
                             Text(desc)
                                 .font(.body)
                                 .foregroundColor(.primary)
-                                .fixedSize(horizontal: false, vertical: true)
+                                .lineLimit(isDescriptionExpanded ? nil : 4)
                                 .textSelection(.enabled)
+                            if desc.count > 250 {
+                                Button(isDescriptionExpanded ? "Less" : "More…") {
+                                    withAnimation(.easeInOut(duration: 0.2)) {
+                                        isDescriptionExpanded.toggle()
+                                    }
+                                }
+                                .font(.callout)
+                                .foregroundStyle(.blue)
+                                .buttonStyle(.plain)
+                            }
                         }
                         .padding(.leading, 4)
                     }