feat: Add Phase 6 for Post-Implementation Review and enhance workflow execution

- Introduced Phase 6: Post-Implementation Review with detailed steps for specialized reviews (quality, security, architecture, action items).
- Updated SKILL.md to reflect new phase and its execution lifecycle.
- Enhanced Flowchart component to conditionally display step statuses based on task tracking.
- Modified TaskDrawer to pass status tracking prop to Flowchart.
- Improved AgentList and other terminal dashboard components for better UI consistency and responsiveness.
- Removed GlobalKpiBar component as part of UI cleanup.
- Added issue detail preview in TerminalWorkbench for better user experience when no terminal is active.
- Updated localization files for new strings related to the terminal dashboard and workbench.
- Enhanced TaskListTab to conditionally render task stats and status dropdown based on task status tracking.

ccw/frontend/src/components/terminal-dashboard/SessionGroupTree.tsx

@@ -96,8 +96,8 @@ export function SessionGroupTree() {
             {formatMessage({ id: 'terminalDashboard.sessionTree.createGroup' })}
           </button>
         </div>
-        <div className="flex-1 flex flex-col items-center justify-center gap-2 text-muted-foreground p-4">
-          <Folder className="w-8 h-8 opacity-50" />
+        <div className="flex-1 flex flex-col items-center justify-center gap-1.5 text-muted-foreground p-4">
+          <Folder className="w-6 h-6 opacity-30" />
           <p className="text-xs text-center">
             {formatMessage({ id: 'terminalDashboard.sessionTree.noGroups' })}
           </p>