feat(ui): add new session icon in sidebar header

packages/ui/src/components/instance/shell/SessionSidebar.tsx

@@ -4,7 +4,7 @@ import type { Session } from "../../../types/session"
 import type { KeyboardShortcut } from "../../../lib/keyboard-registry"
 import type { DrawerViewState } from "./types"
 
-import { Search } from "lucide-solid"
+import { Search, SquarePlus } from "lucide-solid"
 import IconButton from "@suid/material/IconButton"
 import MenuOpenIcon from "@suid/icons-material/MenuOpen"
 import PushPinIcon from "@suid/icons-material/PushPin"
@@ -56,6 +56,20 @@ const SessionSidebar: Component<SessionSidebarProps> = (props) => (
           {props.t("instanceShell.leftPanel.sessionsTitle")}
         </span>
         <div class="flex items-center gap-2 text-primary">
+          <IconButton
+            size="small"
+            color="inherit"
+            aria-label={props.t("sessionList.actions.newSession.ariaLabel")}
+            title={props.t("sessionList.actions.newSession.title")}
+            onClick={() => {
+              const result = props.onNewSession()
+              if (result instanceof Promise) {
+                void result.catch((error) => log.error("Failed to create session:", error))
+              }
+            }}
+          >
+            <SquarePlus class="w-4 h-4 opacity-70" />
+          </IconButton>
           <IconButton
             size="small"
             color="inherit"