feat(settings): host Claude config as a tab in Settings

Settings becomes a tabbed shell (SettingsHub) with one tab per AI tool:
Dashboard (existing settings), Claude Code (CcConfig), plus Codex and
Cursor placeholders. Active tab lives in the ?tool= query param, and the
old /cc-config route redirects to /settings?tool=claude-code. The
standalone sidebar entry is dropped.

Adding a tool is one entry in TOOL_TABS plus its i18n label.

client/src/components/Sidebar.tsx

@@ -58,7 +58,6 @@ import {
   Activity,
   BarChart3,
   Workflow,
-  Boxes,
   Play,
   Settings,
   Wifi,
@@ -91,7 +90,6 @@ const NAV_KEYS = [
   { to: "/sessions", icon: FolderOpen, key: "nav:sessions" },
   { to: "/activity", icon: Activity, key: "nav:activityFeed" },
   { to: "/workflows", icon: Workflow, key: "nav:workflows" },
-  { to: "/cc-config", icon: Boxes, key: "nav:ccConfig" },
   { to: "/run", icon: Play, key: "nav:workspace" },
   { to: "/settings", icon: Settings, key: "nav:settings" },
 ] as const;