docs: add Go inference SDK guide

[think-in-universe]

Add the published Go SDK to the language navigation and SDK overview, with a dedicated Go guide using v0.1.0.

The guide includes a runnable completion-and-receipt-verification example, official OpenAI Go transport integration, streaming completion requirements, E2EE/OHTTP defaults, Gateway/model evidence boundaries, cache lifetimes, errors, and experimental direct endpoints. Link the SDK's verification guide and API reference alongside the runnable examples.

Merge nearai/inference-sdk#101 first: it adds the verification guide targeted by the new links.

Validation:

• The complete quickstart and OpenAI adapter snippet compile against the public-proxy v0.1.0 module with CGO disabled.
• Navigation JSON, changed-page internal links, code fences, and diff checks pass.
• New SDK documentation links and heading anchors checked against the SDK PR checkout.
• Repository broken-link CI passed on the previous revision: https://github.com/nearai/docs/actions/runs/38513188742.
• Local Mintlify validation could not complete because CLI installation repeatedly failed downloading optional agent binaries; stopped the stalled installations.