Document the Helio props and intensity model

[sshdopey]

Context

The Helio components accept motes and intensity props whose meaning lives only in code comments.

Scope

• Document the Helio props, the static-to-live fallback, and the reduced-motion behaviour.

Acceptance criteria

• The Helio API and fallback behaviour are documented.

Pointers

src/brand/Helio.tsx, src/brand/HelioWebGL.tsx, src/brand/LiveHelio.tsx.

[Elizabeth-dev270]

@Elizabeth-dev270 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Allow me fix this pls

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