[Bug]: macOS: qtagg backend crashes on Control-C after input()

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### Bug summary

1. Run the attached code in qtagg on macosx
2. Press Control-C to send a SIGINT.
3. Click on the matplotlib Dock icon.

### Code for reproduction

```Python
import matplotlib
import matplotlib.pyplot as plt
import numpy as np

from matplotlib import cm

# matplotlib.use(backend="TkAgg")

plt.style.use("_mpl-gallery")

# Make data
X = np.arange(-5, 5, 0.25)
Y = np.arange(-5, 5, 0.25)
X, Y = np.meshgrid(X, Y)
R = np.sqrt(X**2 + Y**2)
Z = np.sin(R)

# Plot the surface
fig, ax = plt.subplots(subplot_kw={"projection": "3d"})
ax.plot_surface(X, Y, Z, vmin=Z.min() * 2, cmap=cm.Blues)

ax.set(xticklabels=[], yticklabels=[], zticklabels=[])

plt.show(block=False)

input("Hit [return] to end")
plt.close("all")
```

### Actual outcome

Crash.

[qtagg_crash.txt](https://github.com/user-attachments/files/29781774/qtagg_crash.txt)

### Expected outcome

I'm not 100% what the correct behavior should be, but not a crash. I was thinking that the Control-C would either stop the input() call or immediately close the figure.

### Additional information

_No response_

### Operating system

macOS 14.8

### Matplotlib Version

3.12.0.dev484+g162d8181d.d20260708

### Matplotlib Backend

qtagg

### Python version

3.14.5

### Jupyter version

_No response_

### Installation

None

Start by running the provided Python reproduction with the qtagg backend on macOS, then inspect the qtagg backend involved in handling Control-C during input(). Use qtagg_crash.txt and the reported steps to determine the relevant failure path; done means the reproduction no longer crashes and the resulting interrupt or figure behavior is consistent.

Written by the indexing model from the issue text.