Update ROADMAP_SPEC.md with comprehensive list view type spec compliance evaluation

- Evaluate all 7 list view types (grid, kanban, calendar, gantt, timeline, map, gallery) against @objectstack/spec
- Add navigation property support matrix (width/view gaps across all plugins)
- Document TimelineConfig type alignment gap (dateField vs startDateField)
- Document GalleryConfig type export gap
- Document 10+ missing ListViewSchema spec properties
- Add new critical gaps #11-#15 to section 6.4
- Add new improvement tasks #64-#76 across P1/P2/P3
- Update section 6.1 with detailed per-view-type compliance tables
- Update section 6.3 View Enhancements with TimelineConfigSchema gap

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot