fix(rest): normalize async video mode

[dvd233]

What changed

• Normalize REST's async_mode parameter to the asyncMode field consumed by VideoAPI.
• Keep the normalized flag for the shared response path used by generate_video and image_to_video.
• Add a deterministic node:test regression and expose it through pnpm run test.

Why

The REST tool schema advertises async_mode, but VideoAPI checks asyncMode. Before this change, a REST request with async_mode: true entered the blocking polling/download path instead of returning the submitted task ID. The service could then describe an already completed result as a newly submitted task.

Verification

• pnpm run build
• pnpm run test (1 passed; the baseline test fails before the patch because polling starts)
• git diff --check

The repository-wide pnpm run lint still reports the pre-existing formatting failure in all 20 source files; this focused change does not rewrite unrelated formatting.

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