feat(ui): sidebar redesign — project zones, grouping modes, full-page surfaces (#2480)

* checkpoint: flatten sidebar core (flat sessions, zones, single mode, folders flat)

* checkpoint: sidebar nav + scheduled/archive full-page surfaces, recent zone header

* checkpoint: worktrees management surface via project menu

* checkpoint: docs, i18n, validation for sidebar redesign

* checkpoint: unified row/zone geometry, recent backfill, tooltips everywhere, primary spinner

* checkpoint: branch icon marker, date moved to rich tooltip, recent back to pure time window

* checkpoint: PR state on branch markers + tooltip, no reserved right space, aligned show-more, instant tooltips

* checkpoint: reserve hover-action space so title text is not overlapped

* checkpoint: tighten hover-action reserve

* checkpoint: color-only unread emphasis to avoid title reflow

* checkpoint: drop new-subfolder action, folder actions overlay on hover

* checkpoint: fix sticky project headers (sticky on trigger div), stuck elevation

* checkpoint: full-bleed semibold zone headers, no top scroll fade

* checkpoint: headers without background tint (typography-only emphasis)

* checkpoint: recent header flush with scroll top (no pre-stick bump)

* checkpoint: shared tooltip provider with grouping (instant handoff between rows)

* checkpoint: blur pointer-click focus so hover chrome hides on mouse-leave

* checkpoint: tooltip closeDelay bridges inter-row gap

* checkpoint: nav above controls, merged view dropdown, project-scoped bulk selection, cross-worktree folders

* checkpoint: folder header tooltip with full path name

* checkpoint: true page surfaces (hidden chat, header title, close-on-select), multirun page, run-now jump, folders on top, controls row polish

* checkpoint: rename mode — dual-instance outside-click fix, no vertical shift

* checkpoint: session grouping mode toggle (by-worktree default, flat option)

* checkpoint: worktree header — hover padding reserve + delete worktree action

* checkpoint: frosted sticky header backing under desktop vibrancy

* checkpoint: align worktree sub-header with project header icon column

* checkpoint: restore worktree group DnD reorder; dense vibrancy header tint (Chromium mask+backdrop-filter)

* checkpoint: vibrancy — drop scroller mask so backdrop-filter samples rows (Chromium backdrop-root limitation)

* checkpoint: vibrancy headers use opaque sidebar tone (Electron transparent-window backdrop-filter bug)

* checkpoint: nav collapsed to one row (New session + surface icons), mirrors Add project row

* checkpoint: raise sticky zone headers above row action layers (z-20)

* checkpoint: New session as full-width CTA + single quiet toolbar row

* checkpoint: New session row back to quiet text form above the toolbar

* checkpoint: align toolbar left icon with New session icon column

* checkpoint: hoverless flat header controls (color-only hover states)

* checkpoint: sticky project headers toggle in view dropdown (default on)

* checkpoint: full-page surfaces adapted — archive directory filter panel, scheduled master-detail, multirun without duplicate title bar

* checkpoint: multirun joins mutually exclusive surface set

* checkpoint: surfaces leave via navigation only (no close/cancel buttons), robust close-on-new-session, drop dead MultiRunWindow

* checkpoint: no scheduled header description, aligned empty-worktree note, collapse/expand covers worktree groups

* checkpoint: overlay scrollbar above sticky zone headers

* checkpoint: archive delete icons reveal on hover with padding shift

* checkpoint: new worktrees surface at top of the worktree list

* checkpoint: no grab cursor on worktree headers

* checkpoint: worktrees page list-only with inline action, no worktrees in edit dialog, drop menu ellipsis

* checkpoint: worktrees page uses full content width

* checkpoint: worktrees header — 'in' instead of em dash, no description

* checkpoint: drop legacy OpenCode badge from worktree list, tooltip without OpenCode mention

* review: bound pr summary cache

packages/ui/src/components/session/sidebar/DOCUMENTATION.md

@@ -3,18 +3,16 @@
 ## Refactor result
 
 - `SessionSidebar.tsx` now acts mainly as orchestration; core logic moved to focused hooks/components.
-- Sidebar is now a single multi-project tree: `recent` top section, then projects, then worktrees/archived groups, then sessions.
-- `NavRail` is no longer part of sidebar/navigation flow.
-- Project headers now own root sessions directly; there is no separate rendered `project root` subgroup.
-- Active/hover row styling is text-first; selected sessions use primary text instead of background fills.
-- Archived groups are collapsed by default and support bulk deletion at group/folder level.
-- Session rows support compact inline dates in minimal mode and simplified metadata in default mode.
+- Layout (web/desktop): top navigation (`SidebarNav`: New session, Scheduled, Multi-run, Archive), then the `recent` zone, then one zone per project with a **flat** session list. There is no rendered worktree grouping level.
+- **Two grouping display modes** (`useSessionDisplayStore.sessionGroupingMode`, toggled in the view dropdown): `'by-worktree'` (default) renders the worktree-grouped `sectionsForRender` with slim PR-aware branch sub-headers inside each project zone; `'flat'` renders `flatSectionsForRender` — one merged non-archived group per project (`id: 'flat'`, `folderScopes` listing every contributing scope) with per-row branch markers. Both derive from the same `projectSections` data layer, which alone feeds bootstrap demand planning and PR polling.
+- Project headers are sticky background "zone" bands (`SortableProjectItem`); the `recent` section header uses the same band styling. Collapsed projects show an aggregated busy/unseen indicator (`ProjectAggregateStatusIndicator`), derived from the live status index and notification store scoped to the project's directories.
+- Session rows have a single layout (former `minimal`); the `default`/`minimal` display mode was removed (`session-display-mode` store v4 migration drops the key). Rows show an inline branch label (from `node.worktree` or recent's `secondaryMeta`) when the session lives outside the project root, and bold titles while unread.
+- Folders render **flat** after the loose sessions: nested folders keep `parentId` in the data model but display at one level with a "Parent / Child" path label (`SessionFolderItem.displayName`); collapsing a folder hides its whole subtree. Folder actions resolve their owning scope per folder entry (folders from multiple worktree scopes can coexist under one project).
+- Archived sessions are not shown in the web/desktop sidebar; the Archive page (`ArchiveView`, `useUIStore.isArchivePageOpen`) replaces the old toggle. VS Code keeps inline archived buckets behind `showArchivedSessions` (compact webview has no page surfaces). Unarchive is not possible through the upstream OpenCode HTTP API (`session.update` can only set a finite `time.archived`).
+- Scheduled tasks (`ScheduledTasksDialog`, now a full-page surface on web/desktop) and per-project worktree management (`WorktreesView`, opened from the project menu) render as overlays inside `<main>` in `MainLayout`; the sidebar no longer mounts them.
+- Group-level PR-status polling/indicators and worktree-group drag-to-reorder were removed together with the worktree grouping level; `oc.sessions.groupOrder` is no longer read or written. Worktree PR/branch context lives in the Worktrees surface.
 - Root session menus can quickly create a worktree from the session directory's current branch and move the full session subtree there while idle.
 - Directory loading is demand-driven: the sidebar publishes one complete priority plan for all known project/worktree directories, while the sync layer owns bounded execution.
-- New extractions in latest pass reduced local effect/callback bulk further:
-  - project session list builders
-  - authoritative deletion cleanup
-  - sticky project header observer
 
 ## VS Code grouping
 
@@ -26,14 +24,15 @@
 
 ### Components
 
-- `SidebarHeader.tsx`: Top header UI for add-project, session search, and display mode.
-- `SidebarActivitySections.tsx`: Global top section renderer; currently used for the `recent` section only.
+- `SidebarHeader.tsx`: Top header UI for add-project, session search, selection mode, project sort, and the display menu (recent toggle, collapse/expand all).
+- `SidebarNav.tsx`: Text navigation rows above the tree (New session, Scheduled, Multi-run, Archive); hidden in VS Code.
+- `SidebarActivitySections.tsx`: Global top section renderer; currently used for the `recent` section only, styled as a zone header.
 - `SidebarFooter.tsx`: Static footer with icon-only settings, shortcuts, and about actions.
-- `SidebarProjectsList.tsx`: Main scrollable tree renderer for projects, root sessions, worktrees/groups, and empty/search states.
-- `SessionGroupSection.tsx`: Renders a single worktree/archived group, collapse/expand, folder subtree, group-level controls, and explicit loading/error/retry state for empty groups.
-- `SessionNodeItem.tsx`: Renders one session row/tree node with inline metadata, menu actions, minimal/default variants, and nested children. Rows do not initiate directory bootstrap on mount.
+- `SidebarProjectsList.tsx`: Main scrollable renderer for project zones and their flat/archived groups plus empty/search states; owns project drag-to-reorder.
+- `SessionGroupSection.tsx`: Renders one flat (or archived) group: sessions first, then flat folder entries with path labels, show-more batching, and explicit loading/error/retry state for empty groups. Archived buckets (VS Code) virtualize past 50 rows.
+- `SessionNodeItem.tsx`: Renders one session row/tree node with a single-line layout, inline branch label, indicators, menu actions, and nested children. Rows do not initiate directory bootstrap on mount.
 - `ConfirmDialogs.tsx`: Shared confirm dialog wrappers for session delete and folder delete flows.
-- `sortableItems.tsx`: DnD sortable wrappers for project and group ordering plus project-row action affordances.
+- `sortableItems.tsx`: DnD sortable wrapper for project ordering plus the sticky zone-band project header and its action affordances.
 - `sessionFolderDnd.tsx`: Folder/session DnD scope and wrappers for dropping/moving sessions into folders.
 - `sessionOwnership.ts`: Resolves session directories once into shared project/worktree ownership and folder-scope indexes.
 
@@ -45,7 +44,6 @@
 - `hooks/useSessionGrouping.ts`: Builds grouped session structures and search text/filter helpers.
 - `hooks/useSessionSidebarSections.ts`: Composes final per-project sections and group search metadata for rendering.
 - `hooks/useProjectSessionSelection.ts`: Resolves active/current project-session selection logic and session-directory context.
-- `hooks/useGroupOrdering.ts`: Applies persisted/custom group order with stable fallback ordering; archived groups are reorderable.
 - `hooks/useArchivedAutoFolders.ts`: Maintains archived auto-folder structure and assignment behavior.
 - `hooks/useSidebarPersistence.ts`: Persists sidebar UI state (expanded/collapsed/pinned/group order/active session) to storage + desktop settings.
 - `hooks/useProjectRepoStatus.ts`: Tracks per-project git-repo state and root branch metadata.