Support chat-inline presentation and configurable Atoms script loading in Blaze Web SDK

Extend blaze-sdk-web initialization to support embedded chat checkout presentation .
The SDK should read optional presentationMode from the initialization payload and propagate them through the generated Atoms script element.

Start at the blaze-sdk-web initialization entry point and trace how the initialization payload creates the generated Atoms script element. Verify how optional presentationMode should be propagated for embedded chat checkout and how configurable Atoms script loading is represented. The payload names no file or test, so identify the relevant existing validation before confirming the generated element contains the requested value.

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