Fix strict SSR parsing issues for CubeLayoutButton and highlighting

Description When running server-side static HTML generation using the new middleware-v2 architecture, a few components and guides threw errors during strict isolated node parsing:

1. CubeLayoutButton attempts to read mainContentLayout from viewportController synchronously in construct. In SSR, the button is rendered in the markdown parse stream before having a parent hierarchy, resulting in a TypeError: Cannot read properties of null.
2. The GoogleAuthDemo.md and Authorization.md guides contained env language tokens which are not recognized by highlight.js, causing it to log console.error and crash the strict rendering pipeline.

Proposed Solution

• Add optional chaining (?.) to CubeLayoutButton.mjs viewport controller reference.
• Change ```env to ```bash in the MCP authorization guides.