Show polished loading skeletons the instant a profile switch begins instead of
leaving the previous profile's conversation list and workspace file tree visible
until their fetches resolve (~1s).
- static/style.css: theme-token skeleton system (single-line session rows with
group labels + timestamp bar; tree rows with glyph + name + size bar); subtle
shimmer sweep; dark-mode tokens; prefers-reduced-motion fallback.
- static/sessions.js: showSessionListSkeleton() mirrors real sidebar anatomy
(group headers + single-line rows); _sessionListSkeletonActive flag cleared on
real render.
- static/workspace.js: showWorkspaceTreeSkeleton() mirrors the file-tree row.
- static/panels.js switchToProfile(): clear stale content + show both skeletons
up front; parallelize the independent list + workspace refreshes (Promise.all);
restore real content from cache on switch failure so a skeleton never strands.
Verified live: switch fires -> skeleton instant (0 stale rows) -> resolves to new
profile's real rows. Polished across 1920/1440/1280/390 + dark mode (screenshots
pending Nathan's visual review before gate+PR).
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