macOS Tahoe: Tailscale Network Extension breaks USB Ethernet service for Realtek RTL8153 adapter

### What is the issue?

After upgrading to macOS Tahoe, enabling the Tailscale macOS Network Extension appears to break a USB Ethernet adapter connected through a USB-C hub.

When the Tailscale Network Extension is enabled, Ethernet disappears from System Settings > Network / does not work. Disabling the Tailscale Network Extension and restarting/restoring networking makes Ethernet appear and work again.

This seems related to the macOS Network Extension path rather than the Ethernet adapter itself, because the same hardware works once the Tailscale Network Extension is disabled.

### Environment

- macOS: 26.5
- macOS build: 25F71
- Tailscale version: 1.98.2
- Tailscale build: 101.98.2
- Install type: standalone `/Applications/Tailscale.app`
- Network Extension: `io.tailscale.ipn.macsys.network-extension`
- Network Extension state after disabling: `[activated disabled]`

### Ethernet adapter

USB Ethernet adapter via USB-C hub:

- Product: `USB 10/100/1000 LAN`
- Manufacturer: Realtek
- USB Vendor ID: `0x0bda`
- USB Product ID: `0x8153`
- Chipset appears to be Realtek RTL8153
- Connection: Mac -> USB-C hub -> Ethernet -> switch

When working, macOS exposes it as:

- Network service: `USB 10/100/1000 LAN`
- Device: `en7`
- Link: `1000baseT `
- Status: active

### Steps / observed behavior

1. Upgrade to macOS Tahoe.
2. Use Tailscale 1.98.2 standalone with the Network Extension enabled.
3. Ethernet does not appear/work in System Settings > Network.
4. System Information still sees the USB device as a Realtek `USB 10/100/1000 LAN`.
5. Disable the Tailscale Network Extension from:
`System Settings -> General -> Login Items & Extensions -> Network Extensions`
6. Ethernet appears again and works normally.

### Expected behavior

Tailscale's macOS Network Extension should not prevent a physical USB Ethernet adapter from appearing or working.

### Actual behavior

With the Tailscale Network Extension enabled, the USB Ethernet service disappears / fails to work. Disabling the Tailscale Network Extension restores Ethernet.

### Notes

This may be related to other Tahoe/macOS Network Extension issues, but this specific symptom involves a physical Realtek RTL8153 USB Ethernet adapter disappearing/failing while Tailscale's Network Extension is enabled.