Fix AttachProcessDialog leak causing DebuggerController ref leak

[xusheng6]

Summary

• AttachProcessDialog was heap-allocated with new but never freed in the attach action handler (ui/ui.cpp)
• Since it owns a ProcessListWidget which holds a DbgRef<DebuggerController>, this also caused the controller to leak
• Added deleteLater() on all exit paths after the dialog is used

Test plan

• Open a binary, attach to a process via the debugger, then stop debugging and close the file
• Verify no DebuggerController leak is reported in the leak detector

Fix #1061

🤖 Generated with Claude Code

[plafosse]

Why allocate at all?

AttachProcessDialog dialog(context->mainWindow(), controller);
if (dialog.exec() != QDialog::Accepted)
    return;

uint32_t pid = dialog.GetSelectedPid();
if (pid == 0)
    return;

[xusheng6]

Why allocate at all?

AttachProcessDialog dialog(context->mainWindow(), controller);

if (dialog.exec() != QDialog::Accepted)

    return;



uint32_t pid = dialog.GetSelectedPid();

if (pid == 0)

    return;

Good point -- let me fix that