Brief: Sidebar sections with more than 20 links collapse via HTML details/summary to keep the sidebar manageable as the wiki grows.

Context

As the wiki grows, sections like Decisions or Entities can accumulate many pages, making the sidebar unwieldy and requiring excessive scrolling.

Decision

In base.html, any nav section whose page count exceeds 20 renders as a <details class="nav-section"> element with a <summary> header instead of a plain <h4>. Smaller sections remain unchanged. A small inline DOMContentLoaded script reopens the <details> block that contains the currently active page, so navigation context is never lost.

Consequences

• Sidebar stays compact by default for large sections.
• The active section always opens automatically — no manual hunting.
• Zero build-time cost; purely a template + CSS change.
• The threshold (20) is a constant in the Jinja2 template. If it needs to be configurable, it could be passed as a template variable from builder.py.

Alternatives Rejected

• JavaScript-only toggle: adds complexity without benefit since <details> is native HTML with no dependencies.
• Always collapsed: bad UX — users would always need an extra click even for small sections.