docs(nodes): fill node/SDK reference content gaps from CodeRabbit review

[joshuadarron]

Context

Low-value content nits surfaced by CodeRabbit on #1213, deferred out of the review commits. Each is a small prose addition/edit.

Tasks

• nodes/src/nodes/embedding_openai/doc.md — document the questions input lane in prose (it appears in the generated reference but is never explained).
• nodes/src/nodes/llm_anthropic/doc.md — document the claude-opus-4-7 profile that appears in the generated section but not the prose.
• nodes/src/nodes/audio_tts/doc.md — soften/remove the internal "BEGIN / WRITE / END" protocol detail from user-facing prose.
• packages/client-python/docs/index.md — clarify URI scheme guidance (examples mix https:// and wss://cloud.rocketride.ai).

Acceptance

Each box addressed; builder docs:build stays green. (Generated <!-- ROCKETRIDE:GENERATED:PARAMS --> blocks are not hand-edited — only surrounding prose.)

Refs: PR #1213.

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