Fix Cloudflare tunnel crash errors when stopping app dev on Windows - #9065

WHY are these changes introduced?

Stopping a working app dev session on Windows can report that the Cloudflare tunnel crashed. The final process-tree cleanup kills the tunnel without marking its exit as an expected stop.

WHAT is this pull request doing?

Stop the managed tunnel through the dev session's abort signal before process-tree cleanup. Also release it when preparation, process setup, or the session fails. Keep reporting unexpected tunnel failures.

No changeset is included in this PR; the stable/5.0 PR includes one.

How to manually test your changes?

1. On Windows, run pnpm shopify app dev --path <app-directory> from this checkout with a linked app.
2. Wait for the tunnel to connect and confirm that the app preview works.
3. Press q. Confirm that the session stops without the Cloudflare "process crashed after stablishing a connection" error.
4. Start the session again and stop it with Ctrl+C. Confirm the same result.

Validation

• Five new lifecycle regression cases fail before the fix and pass after it.
• 86 related tests pass, including the subprocess shutdown tests.
• App type check, changed-file ESLint, and Prettier checks pass.
• Live Windows validation is not yet complete.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type and added a changeset