Bind mapped stub-task arguments in the TypeScript SDK runtime

### Background

https://github.com/apache/airflow/pull/70570 makes the execution API derive a **per-map-index** arg-binding spec for a dynamically mapped `@task.stub`. https://github.com/apache/airflow/pull/70571 implements the Go-SDK consumer; the TypeScript SDK has neither the mapped consumer nor the unmapped one yet, so this work assumes the TypeScript arg-binding consumer for unmapped stub calls lands first.

`XComArgBinding` carries two selectors the unmapped path never sets:

- `map_index` — pull the upstream XCom row at that index (expand over a *mapped* upstream).
- `element_index` — pull the unmapped upstream row, then take element N of the resulting sequence (expand over an *unmapped* upstream's list output).

Literal expands are resolved to their element server-side and arrive as plain literals, so the binding surface itself is unchanged from the unmapped case.

Note that the generated `ts-sdk/src/generated/supervisor.ts` models are regenerated as part of the upstream schema bump, so the types should already be present; only the runtime resolution is missing.

### What needs to happen

1. Extend the TypeScript runtime's arg-binding resolution to honour `map_index` and `element_index`, with typed and out-of-range errors that fail the task before the handler runs.
2. Keep the unmapped path unchanged: a binding with neither selector takes the whole value.
3. Add a mapped example to the TypeScript example bundle and cover it with an Airflow-level integration test, alongside the existing coordinator-mode tests.

### Acceptance criteria

- A `@task.stub` expanded with `.expand()` delivers the correct per-index element to the TypeScript handler for all three expand forms (literal collection, unmapped upstream's list output, mapped upstream).
- Multiple expanded kwargs (the cross product) bind correctly, including mixed expand sources in one call.
- `.partial()` literals and unmapped-upstream XComs bind identically on every index.
- Out-of-range or type-mismatched selectors reject loudly instead of silently passing `undefined`.

### Context

- Depends on https://github.com/apache/airflow/pull/69757 and https://github.com/apache/airflow/pull/70570, plus the TypeScript arg-binding consumer for unmapped stub calls
- Go parallel: https://github.com/apache/airflow/pull/70571