Add searchable rules reference to the DM Screen

[Daren9m]

Summary

• add a native Rules Reference element to the DM Screen
• provide 33 searchable and independently collapsible 2024/SRD 5.2.1 references
• cover conditions, saving throws and DCs, common combat actions, cover, concentration, death saves, recovery, movement, and visibility
• include the reference by default on new DM screens while allowing existing screens to add, hide, collapse, rename, or remove it
• include the complete reference in Markdown and print exports
• add focused coverage for condition completeness, filtering, and DM Screen export behavior

Why

DMs need fast access to frequently checked rules without leaving their live session workspace. Keeping the reference as a normal DM Screen element preserves the screen's configurable, collapsible design and lets it travel with exported session material.

User impact

New DM screens start with a ready-to-use Quick Reference section. Existing saved screens can add the element through the screen builder without losing any existing state.

Validation

• npm test — 701 tests passed
• npm run lint
• npm run typecheck
• npm run build
• local browser interaction check for adding the element, searching, filtering, collapsing, and rendering; no browser errors