refactor: modularize session sidebar and add GitHub PR tracking (#610)

* feat: switch sessions sidebar to global paginated loading with archived flow

Load sessions via global endpoint with progressive 500-item pagination and legacy fallback
Add dedicated archived sidebar section for archived and unassigned sessions
Change remove behavior to archive outside archived and hard-delete inside archived

* feat: improve archived sessions UX and folder persistence

Archive sessions on worktree removal while keeping worktree deletion
Streamline archived sidebar actions, icons, metadata, and tooltips
Persist session folders to ~/.config/openchamber/sessions-directories.json with startup hydration

* fix: align archived session actions and clean empty archived folders

Apply archived dropdown behavior consistently for folder-contained sessions
Remove archived-only folder actions while keeping standard folder behavior elsewhere
Auto-prune empty archived folders during session cleanup and persistence sync

* refactor: modularize session sidebar and stabilize behavior

Split monolithic sidebar logic into focused hooks and components
Kept session, archive, folder, and project interactions working with cleaner state persistence
Added sidebar DOCUMENTATION.md summarizing file roles and refactor outcomes

* fix: improve fork PR detection and smart remote tracking

Added centralized PR status store for shared polling and refresh
Auto-selects the remote that has an existing PR when current remote has none
Stops periodic polling for closed or merged PRs to reduce unnecessary requests

* fix: make chat and toast corners follow active theme radius

Toast corners now use theme radius tokens instead of hardcoded rounding
User message bubble now uses theme-configured max radius with preserved tail corner
Square-corner themes now consistently affect both toasts and chat bubbles

* feat: show live PR status across git view and session sidebar

Added a shared GitHub PR status store with adaptive background polling and terminal-state pause
Improved fork remote detection and auto-selection so existing PRs are found more reliably
Updated session group headers to show clickable PR number with branch and state-colored branch icon

* feat: centralize GitHub PR tracking and enrich session sidebar PR details

Moved PR status polling to a single global pipeline keyed by directory and branch
Improved fork-aware PR resolution and reduced duplicate GitHub status fetches across views
Added richer session sidebar PR display with clickable number, state-aware styling, and structured tooltip details

* fix: adjust PR indicator icon vertical alignment

Fine-tuned PR indicator icon vertical alignment in session sidebar
Reduced icon translate-y from 2px to 0.5px for better visual balance

* feat: improve session sidebar status display

* feat: enhance session display logic for minimal mode and improve dropdown menu accessibility

* feat: refactor session row to include tooltip for minimal display mode

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

@@ -0,0 +1,46 @@
+# Session Sidebar Documentation
+
+## Refactor result
+
+- `SessionSidebar.tsx` now acts mainly as orchestration; core logic moved to focused hooks/components.
+- Sidebar behavior stays intact: global+archived session grouping, folder operations, delete/archive semantics, project/worktree rendering, and search.
+- Recent migration gaps were fixed (persistence + repo-status hooks fully wired).
+- New extractions in latest pass reduced local effect/callback bulk further:
+  - project session list builders
+  - folder cleanup sync
+  - sticky project header observer
+- Baseline checks pass after refactor: `type-check`, `lint`, `build`.
+
+## File summaries
+
+### Components
+
+- `SidebarHeader.tsx`: Top header UI (project selector/rename, search, add/open actions, notes/worktree entry points).
+- `SidebarProjectsList.tsx`: Main scrollable list renderer for project sections/groups, empty states, and project-level interactions.
+- `SessionGroupSection.tsx`: Renders a single group (root sessions + folders), collapse/expand, and group-level controls.
+- `SessionNodeItem.tsx`: Renders one session row/tree node with metadata, menu actions, inline rename, and nested children.
+- `ConfirmDialogs.tsx`: Shared confirm dialog wrappers for session delete and folder delete flows.
+- `sortableItems.tsx`: DnD sortable wrappers for project and group ordering with drag handles/overlays.
+- `sessionFolderDnd.tsx`: Folder/session DnD scope and wrappers for dropping/moving sessions into folders.
+
+### Hooks
+
+- `hooks/useSessionActions.ts`: Centralizes session row actions (select/open, rename, share/unshare, archive/delete, confirmations).
+- `hooks/useSessionSearchEffects.ts`: Handles search open/close UX and input focus behavior.
+- `hooks/useSessionPrefetch.ts`: Prefetches messages for nearby/active sessions to improve perceived load speed.
+- `hooks/useDirectoryStatusProbe.ts`: Probes and caches directory existence status for session/path indicators.
+- `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.
+- `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.
+- `hooks/useProjectSessionLists.ts`: Builds live and archived session lists for a given project (including worktrees + dedupe).
+- `hooks/useSessionFolderCleanup.ts`: Cleans stale folder session IDs by reconciling known sessions/archived scopes.
+- `hooks/useStickyProjectHeaders.ts`: Tracks which project headers are sticky/stuck via `IntersectionObserver`.
+
+### Types and utilities
+
+- `types.ts`: Shared sidebar types (`SessionNode`, `SessionGroup`, summary/search metadata).
+- `utils.tsx`: Shared sidebar utilities (path normalization, sorting, dedupe, archived scope keys, project relation checks, text highlight, labels).