Fix Function replay shutdown and process cancellation - #9057

WHY are these changes introduced?

Cancelling Function replay must stop active runner processes and queued rebuilds before replay finishes.

WHAT is this pull request doing?

Cancel active runner processes and build-lock waits, prevent queued builds from starting after cancellation, and wait for active work and watcher cleanup before the final cancellation record. Remove process abort listeners after execution. Stop the replay-local scan and startup change waiters, including when stop is called without an abort signal.

This PR follows #9108, which follows #9056. Its diff contains shutdown behavior and tests. The JSON feature and broader startup refactor remain in the preceding PRs. Preserve the readiness opt-out while adding shutdown cleanup.

How to manually test your changes?

Use a test app with a Function and a saved Function log.

1. Run pnpm shopify app function replay --path <function-directory> --log <log-id> --json --no-input.
2. Edit the Function to start a rebuild. Press Ctrl-C while the build or runner is active. Check that active work stops, the final record is cancelled, and the command exits with code 130.
3. Repeat with a build waiting for another process to release .build-lock. Cancel replay, then release the lock. Check that no new build starts.
4. Repeat without --json to check text replay. Use --no-watch --json to check single-result output.

Validation

• 408 related Function, replay, watcher, startup, build cancellation, and dev session tests passed on the rebased head.
• All 11 subprocess cancellation tests passed.
• App type checking, scoped ESLint, formatting, and diff checks passed. The rebase retains the readiness opt-out and the shared startup state handling.
• Local checks ran on macOS ARM with Node 24.22.1. Native probes use a controlled runner capture.

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 and has changesets.