Templates page is now a tree-only browser; editing happens on a dedicated
TemplateEdit page. Drag-drop is replaced by context-menu Move-to-Folder.
TreeView gains Bootstrap Icons (chevron + per-kind glyphs), ancestor guide
lines, defined hover/selected/focus tokens, and Escape-dismisses-menu per
the new Visual Design Guide (V1-V7) in Component-TreeView.md.