refactor: Hybrid chapter pages — index by default, inline text on demand

[williamzujkowski]

Problem

Chapter pages like Title 6 Ch. 1 (341 sections) render ALL statutory text inline, causing slow loads and mobile layout issues.

Proposal (consensus 2-1)

Convert to hybrid: index view by default (LII pattern), "Read full chapter" toggle loads inline text on demand.

Default view (index)

• Section list with links (like current title TOC but at chapter level)
• Fast loads, clean mobile layout

Toggle view (inline text)

• Current full-text experience preserved
• Loaded on demand (client-side fetch or hidden HTML revealed)
• Only for users who specifically want to read in flow

References

• Cornell LII chapter pages (index-only)
• CSS fixes for mobile overflow already shipped (PRs fix(mobile): Responsiveness for chapter pages and statutory text #138, fix(mobile): Critical fixes — overflow, indentation, sticky headers #142, fix(mobile): Heading sizes, TOC scroll, prev/next truncation #143)