refactor(sidebar): remove dead directoryStatus probe artifact (#1660)

Commit 7205d7a3 replaced runtime directory probing with buildKnownSessionDirectories

filtering, but left the hook, prop, state, and UI checks as a transitional artifact.

- Delete useDirectoryStatusProbe.ts

- Remove directoryStatus state/prop from SessionSidebar, SessionGroupSection, SessionNodeItem

- Remove isMissingDirectory checks, opacity-75 styling, and disabled states

- Simplify handleSessionSelect signature

- Update sidebar DOCUMENTATION.md

Co-authored-by: Leonid Skorobogatyy <bash@opencode.itc.local>

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

@@ -39,7 +39,6 @@
 - `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.