Persist project/worktree expand state across restarts and decouple it from
the active directory — projects default expanded, worktree groups collapsed,
and the user's explicit toggles are remembered.
Selecting a session now switches the active project (not just the draft),
following the session's directory.
Replace all-or-nothing session pagination with incremental +7 loading that
resets when a group or project is toggled, matching the desktop sidebar.
Always render root (project-level) sessions as a flat list above worktree
groups, and vertically center the session row status dot.
Bohdan Triapitsyn
51682dc7af