Add accordion menus for long-form content pages

[rdhyee]

Context

Hana left 3 separate comments on the April 3 wireframe requesting accordion/collapsible menus on the Architecture & Vocabularies, Requirements, and Vocabularies pages. These pages have dense text content that would benefit from progressive disclosure.

Pages affected

• Architecture & Vocabularies → Overview section
• Requirements → 17 requirement descriptions (currently all expanded)
• Vocabularies → 12+ vocabulary descriptions

Implementation

Quarto supports collapsible callouts natively:
```markdown
::: {.callout-note collapse="true"}

Mint Identifiers

Mint identifiers and manage record...
:::
```

Alternatively, HTML <details>/<summary> elements work in Quarto and give a clean accordion pattern with no JS required.

Figma reference

iSamples Wireframe 1.0 — comments on Architecture, Requirements, Vocabularies frames

[rdhyee]

Completed in PR #90 (accordion menus for Requirements page) and PR #93 (vocabularies cleanup).