TypeScript SDK: add a `ts pack` bundle build tool

[jason810496]

Background

Users of the TypeScript task SDK currently have to run esbuild by hand and hand-write the airflow-metadata.yaml sidecar next to the bundle. Folding metadata generation into the build tooling was deferred to a follow-up in #68548 and #69079.

What needs to happen

1. Add a ts pack (or similar) CLI tool that bundles TypeScript handlers into a single bundle.mjs via esbuild.
2. Auto-generate airflow-metadata.yaml from the handler registry.
3. Combine the .mjs and metadata into a single artifact to avoid drift between the two files.

Acceptance criteria

• One command produces a deployable TypeScript bundle with correct metadata.
• No hand-written metadata sidecar is needed.

Context

• Add NodeCoordinator #68548 (PR description)
• Add TypeScript coordinator runtime #69079 (PR description)
• Single-artifact review thread: Add NodeCoordinator #68548 (comment), deferred in Add NodeCoordinator #68548 (comment)

[guan404ming]

Coooool one, I would like to help with this!