fix(ui): report failed paste/drop in the interactive terminal

PasteAsync silently swallowed every exception and returned void, so a
package update renaming Iciclecreek's private write seam would break
Ctrl+V/drop with zero user-visible signal. PasteAsync/SendTextAsync now
return bool (mirroring SendLineAsync), and the view checks the result,
routing a failure through InteractiveTerminalViewModel.ErrorReported ->
ConPtyPaneViewModel.ErrorReported -> the existing footer error strip.

src/ClaudeDo.Ui/Services/PtyTerminalSession.cs

@@ -162,15 +162,19 @@ public sealed class PtyTerminalSession : IDisposable
     /// writing the clipboard text raw, because that is what honours bracketed-paste mode — without
     /// it a multi-line paste is read line by line and submits on the first newline.
     /// </summary>
-    public async Task PasteAsync()
+    public async Task<bool> PasteAsync()
     {
-        if (_control is not { } control || !IsRunning) return;
+        if (_control is not { } control || !IsRunning) return false;
         try
         {
-            if (s_terminalViewField?.GetValue(control) is TerminalView view)
-                await view.PasteAsync();
+            if (s_terminalViewField?.GetValue(control) is not TerminalView view) return false;
+            await view.PasteAsync();
+            return true;
+        }
+        catch (Exception)
+        {
+            return false;
         }
-        catch (Exception) { /* best-effort, same as SendLineAsync */ }
     }
 
     // Long enough that the two writes can't be read as one chunk by the child's stdin reader.