[General] In the left panel, on the [Group By] filter, it will be nice to have the filt...

**Mood:** 😊
**Category:** General

## Goal
Improve the left-sidebar **Group by** experience so users can group sessions by status **and** optionally narrow the list to one or more specific statuses.

## Problem
Today, the sidebar menu allows selecting **Group by = Status**, but it does not allow refining to specific status values (for example only **Open** or only **Working**). This makes the grouped view less useful when many sessions are present.

## Proposed UX
1. Keep **Group by** as a layout choice (Project / Status / Last updated).
2. Add a **Status filter** control for sidebar sessions.
3. Allow selecting specific values (example: Open, Working), with an **All statuses** default.
4. If **Group by = Status**, still show status groups, but only for the selected filtered values.
5. Persist the chosen filter and make active filtering visually clear.

## Why this helps
- Faster triage when many sessions are visible.
- Better focus on active work without switching to a different view.
- More consistent behavior with other filterable surfaces in the app.

## Suggested acceptance criteria
- User can select one or more status values from the sidebar filter.
- Sidebar content updates correctly in all group modes.
- Group-by-status view only displays selected status groups.
- Clearing filter returns to all statuses.
- Filter state persists across navigation/restart.
- Keyboard and screen-reader interaction works for the new filter controls.

## Test notes
- Verify on Windows first (reported environment), then macOS/Linux sanity pass.
- Validate behavior with large session lists and mixed statuses.

---
| Field | Value |
| --- | --- |
| App version | 1.0.10 |
| OS | Windows 10.0.26300 |
| Theme | GitHub |
| Path | /mywork |
| Tenure | Week 7 |

左サイドバーの Group by コントロールから始め、既存のセッションのグループ化とフィルターの動作を追跡します。サイドバーの状態がどのように保持されるか、またフィルターコントロールがキーボードとスクリーンリーダーでの操作をどのようにサポートしているかを確認します。提案されたステータス選択がすべてのグループモードで機能し、ナビゲーションと再起動をまたいで保持され、macOS/Linux でのサニティチェックを含む Windows-first テストに合格すれば完了です。

索引モデルが issue の本文から書いたものです。