TypeScript SDK: Dag/task-aware multi-bundle selection in NodeCoordinator

[jason810496]

Background

NodeCoordinator currently uses a simple ordered-fallback strategy: bundles_root is scanned and the first valid bundle is selected. Dag/task-aware selection across multiple TypeScript bundles was deliberately deferred until the bundle tooling exists.

What needs to happen

1. Extend NodeCoordinator bundle selection to route by Dag/task across multiple TypeScript bundles.
2. Depends on the bundle tooling in TypeScript SDK: add a ts pack bundle build tool #69286.

Acceptance criteria

• Multiple TypeScript bundles under bundles_root can coexist, with tasks routed to the right bundle by Dag/task ID.

Context

• Add NodeCoordinator #68548 (PR description)