bug: Amazon Q Desktop fails during first launch with "Failed to update" (macOS Tahoe 26.4.1)

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

macOS Tahoe 26.4.1

### Expected behaviour

downloaded the official Amazon Q Desktop DMG from AWS and installed it on a clean macOS system.

On first launch, I expected Amazon Q Desktop to:

1. Start successfully.
2. Show the welcome/sign-in screen.
3. Complete the initial setup.
4. Allow shell integration installation.
5. Allow Accessibility permissions.
6. Start normally without attempting to update immediately.

The application should not fail during its first launch.

### Actual behaviour

Immediately after launching Amazon Q Desktop, the application displays:

Amazon Q is updating

followed by:

failed to update

The application then exits.

Launching the application directly from Terminal provides additional information:

```text
Failed to swap app bundle:
Directory not empty (os error 66)

failed to swap app bundle, trying to elevate permissions

Failed to update

The application never reaches the sign-in or onboarding screen.

## **Output of `q doctor`**

```markdown
Unable to run.

The desktop application exits during its first launch before the CLI is available.

Running:

q doctor

is not possible because the `q` command is never installed or exposed.

### Steps to reproduce

1. Download the latest Amazon Q Desktop installer from:

https://desktop-release.q.us-east-1.amazonaws.com/latest/Amazon%20Q.dmg

2. Mount the DMG.

3. Drag "Amazon Q.app" into the /Applications folder.

4. Launch Amazon Q from Applications (or using `open -a "Amazon Q"`).

5. Instead of displaying the sign-in/onboarding screen, the application immediately starts its self-update process.

6. The updater displays:

Amazon Q is updating

followed by:

failed to update

7. Launching the application directly from Terminal:

```bash
"/Applications/Amazon Q.app/Contents/MacOS/q_desktop"
```

produces:

```text
Failed to swap app bundle:
Directory not empty (os error 66)

failed to swap app bundle, trying to elevate permissions

Failed to update
```

8. The application exits before the onboarding or sign-in screen is displayed.

The issue is reproducible every time after a fresh installation.

### Environment

```yaml
Unable to run `q diagnostic` because the issue occurs before the Amazon Q CLI becomes available.

Environment:

- macOS Tahoe 26.4.1
- Apple Silicon (ARM64)
- GNU Bash 5.3.15
- iTerm2
- Fresh installation
- Official installer downloaded from AWS
- No previous Amazon Q installation
- No previous Fig installation

Additional observations:

- Amazon Q launches successfully.
- The application immediately starts its self-update process.
- The updater fails with:

Failed to swap app bundle:
Directory not empty (os error 66)

- The application exits immediately afterward.
- Because the application never completes its first launch, `q`, `q doctor`, `q restart`, and `q diagnostic` are unavailable.
```

Reproduce the failure from a clean DMG installation on macOS Tahoe, then start at /Applications/Amazon Q.app/Contents/MacOS/q_desktop and trace the self-update path that reports the bundle swap error. Done means a fresh first launch reaches the onboarding or sign-in screen without exiting after the update attempt.

Written by the indexing model from the issue text.