fix(desktop): migrate old tab paths + fix shell slug deadlock

Tab store rehydration: old-format paths like "/issues/abc" (missing
workspace slug prefix) are reset to "/" so IndexRedirect picks the
correct workspace. Detection: if the first segment is a known route
name (issues, projects, etc.) rather than a workspace slug, it's an
old-format path.

Desktop shell: TabContent must always render (not gated behind slug
check) so WorkspaceRouteLayout can mount and call setCurrentWorkspace.
Only sidebar and shell-level UI (chat, modals, search) gate on slug
being present.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/desktop/src/renderer/src/components/desktop-layout.tsx

@@ -15,7 +15,6 @@ import { ChatFab, ChatWindow } from "@multica/views/chat";
 import { StepWorkspace } from "@multica/views/onboarding";
 import { WorkspaceSlugProvider } from "@multica/core/paths";
 import { getCurrentSlug, subscribeToCurrentSlug } from "@multica/core/platform";
-import { MulticaIcon } from "@multica/ui/components/common/multica-icon";
 import { DesktopNavigationProvider } from "@/platform/navigation";
 import { OnboardingGate } from "./onboarding-gate";
 import { TabBar } from "./tab-bar";
@@ -105,31 +104,31 @@ export function DesktopShell() {
           </div>
         )}
       >
-        {slug ? (
-          <WorkspaceSlugProvider slug={slug}>
-            <div className="flex h-screen">
-              <SidebarProvider className="flex-1">
-                <AppSidebar topSlot={<SidebarTopBar />} searchSlot={<SearchTrigger />} />
-                {/* Right side: header + content container */}
-                <div className="flex flex-1 min-w-0 flex-col">
-                  <MainTopBar />
-                  {/* Content area with inset styling — relative so ChatWindow/ChatFab are constrained here */}
-                  <div className="relative flex flex-1 min-h-0 flex-col overflow-hidden mr-2 mb-2 ml-0.5 rounded-xl shadow-sm bg-background">
-                    <TabContent />
-                    <ChatWindow />
-                    <ChatFab />
-                  </div>
+        {/* WorkspaceSlugProvider accepts null — components that need slug
+            use useWorkspaceSlug() (nullable) or useRequiredWorkspaceSlug()
+            (throws). TabContent MUST always render so the tab router can
+            mount WorkspaceRouteLayout, which calls setCurrentWorkspace()
+            to populate the slug. The sidebar gates on slug being present
+            to avoid the useRequiredWorkspaceSlug throw. */}
+        <WorkspaceSlugProvider slug={slug}>
+          <div className="flex h-screen">
+            <SidebarProvider className="flex-1">
+              {slug && <AppSidebar topSlot={<SidebarTopBar />} searchSlot={<SearchTrigger />} />}
+              {/* Right side: header + content container */}
+              <div className="flex flex-1 min-w-0 flex-col">
+                <MainTopBar />
+                {/* Content area with inset styling — relative so ChatWindow/ChatFab are constrained here */}
+                <div className="relative flex flex-1 min-h-0 flex-col overflow-hidden mr-2 mb-2 ml-0.5 rounded-xl shadow-sm bg-background">
+                  <TabContent />
+                  {slug && <ChatWindow />}
+                  {slug && <ChatFab />}
                 </div>
-              </SidebarProvider>
-            </div>
-            <ModalRegistry />
-            <SearchCommand />
-          </WorkspaceSlugProvider>
-        ) : (
-          <div className="flex h-screen items-center justify-center">
-            <MulticaIcon className="size-6 animate-pulse" />
+              </div>
+            </SidebarProvider>
           </div>
-        )}
+          {slug && <ModalRegistry />}
+          {slug && <SearchCommand />}
+        </WorkspaceSlugProvider>
       </OnboardingGate>
     </DesktopNavigationProvider>
   );

apps/desktop/src/renderer/src/stores/tab-store.ts

@@ -199,12 +199,28 @@ export const useTabStore = create<TabStore>()(
           | undefined;
         if (!persisted?.tabs?.length) return currentState;
 
-        const tabs: Tab[] = persisted.tabs.map((tab) => ({
-          ...tab,
-          router: createTabRouter(tab.path),
-          historyIndex: 0,
-          historyLength: 1,
-        }));
+        const tabs: Tab[] = persisted.tabs.map((tab) => {
+          // Migration: pre-refactor tab paths like "/issues/abc" lack a
+          // workspace slug prefix. These would 404 in the new router.
+          // Reset to "/" so IndexRedirect picks the right workspace.
+          let path = tab.path;
+          if (path !== "/" && !isGlobalPath(path)) {
+            const segments = path.split("/").filter(Boolean);
+            const firstSegment = segments[0] ?? "";
+            // If the first segment IS a known route name (e.g. "issues",
+            // "projects"), it's an old-format path missing the slug prefix.
+            if (ROUTE_ICONS[firstSegment]) {
+              path = "/";
+            }
+          }
+          return {
+            ...tab,
+            path,
+            router: createTabRouter(path),
+            historyIndex: 0,
+            historyLength: 1,
+          };
+        });
 
         // Validate activeTabId — fall back to first tab if stale
         const activeTabId = tabs.some((t) => t.id === persisted.activeTabId)