fix: Resolve all ESLint errors and warnings in web package

Fixes all 542 ESLint problems in the web package to achieve 0 errors and 0 warnings.

Changes:
- Fixed 144 issues: nullish coalescing, return types, unused variables
- Fixed 118 issues: unnecessary conditions, type safety, template literals
- Fixed 79 issues: non-null assertions, unsafe assignments, empty functions
- Fixed 67 issues: explicit return types, promise handling, enum comparisons
- Fixed 45 final warnings: missing return types, optional chains
- Fixed 25 typecheck-related issues: async/await, type assertions, formatting
- Fixed JSX.Element namespace errors across 90+ files

All Quality Rails violations resolved. Lint and typecheck both pass with 0 problems.

Files modified: 118 components, tests, hooks, and utilities

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/web/src/app/(auth)/callback/page.test.tsx

@@ -7,11 +7,11 @@ const mockPush = vi.fn();
 const mockSearchParams = new Map<string, string>();
 
 vi.mock("next/navigation", () => ({
-  useRouter: () => ({
+  useRouter: (): { push: typeof mockPush } => ({
     push: mockPush,
   }),
-  useSearchParams: () => ({
-    get: (key: string) => mockSearchParams.get(key),
+  useSearchParams: (): { get: (key: string) => string | undefined } => ({
+    get: (key: string): string | undefined => mockSearchParams.get(key),
   }),
 }));
 

apps/web/src/app/(auth)/login/page.test.tsx

@@ -4,7 +4,7 @@ import LoginPage from "./page";
 
 // Mock next/navigation
 vi.mock("next/navigation", () => ({
-  useRouter: () => ({
+  useRouter: (): { push: ReturnType<typeof vi.fn> } => ({
     push: vi.fn(),
   }),
 }));

apps/web/src/app/(authenticated)/knowledge/page.tsx

@@ -53,8 +53,10 @@ export default function KnowledgePage(): ReactElement {
       filtered = filtered.filter(
         (entry) =>
           entry.title.toLowerCase().includes(query) ||
-          entry.summary?.toLowerCase().includes(query) ||
-          entry.tags.some((tag: { name: string }) => tag.name.toLowerCase().includes(query))
+          (entry.summary?.toLowerCase().includes(query) ?? false) ||
+          entry.tags.some((tag: { name: string }): boolean =>
+            tag.name.toLowerCase().includes(query)
+          )
       );
     }
 
@@ -85,7 +87,7 @@ export default function KnowledgePage(): ReactElement {
   );
 
   // Reset to page 1 when filters change
-  const handleFilterChange = (callback: () => void) => {
+  const handleFilterChange = (callback: () => void): void => {
     callback();
     setCurrentPage(1);
   };
@@ -93,7 +95,7 @@ export default function KnowledgePage(): ReactElement {
   const handleSortChange = (
     newSortBy: "updatedAt" | "createdAt" | "title",
     newSortOrder: "asc" | "desc"
-  ) => {
+  ): void => {
     setSortBy(newSortBy);
     setSortOrder(newSortOrder);
     setCurrentPage(1);

apps/web/src/app/(authenticated)/settings/workspaces/[id]/page.tsx

@@ -86,9 +86,13 @@ export default function WorkspaceDetailPage({
   const [workspace, setWorkspace] = useState<Workspace>(mockWorkspace);
   const [members, setMembers] = useState<WorkspaceMemberWithUser[]>(mockMembers);
   const currentUserId = "user-1"; // TODO: Get from auth context
-  const currentUserRole = WorkspaceMemberRole.OWNER; // TODO: Get from API
+  const currentUserRole: WorkspaceMemberRole = WorkspaceMemberRole.OWNER; // TODO: Get from API
 
-  const canInvite = currentUserRole === WorkspaceMemberRole.OWNER || currentUserRole === WorkspaceMemberRole.ADMIN;
+  // TODO: Replace with actual role check when API is implemented
+  // Currently hardcoded to OWNER in mock data (line 89)
+  const canInvite =
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+    currentUserRole === WorkspaceMemberRole.OWNER || currentUserRole === WorkspaceMemberRole.ADMIN;
 
   const handleUpdateWorkspace = async (name: string): Promise<void> => {
     // TODO: Replace with real API call

apps/web/src/app/(authenticated)/settings/workspaces/page.tsx

@@ -41,12 +41,12 @@ export default function WorkspacesPage(): ReactElement {
     const membership = mockMemberships.find((m) => m.workspaceId === workspace.id);
     return {
       ...workspace,
-      userRole: membership?.role || WorkspaceMemberRole.GUEST,
-      memberCount: membership?.memberCount || 0,
+      userRole: membership?.role ?? WorkspaceMemberRole.GUEST,
+      memberCount: membership?.memberCount ?? 0,
     };
   });
 
-  const handleCreateWorkspace = async (e: React.SyntheticEvent<HTMLFormElement>) => {
+  const handleCreateWorkspace = async (e: React.SyntheticEvent<HTMLFormElement>): Promise<void> => {
     e.preventDefault();
     if (!newWorkspaceName.trim()) return;
 

apps/web/src/app/(authenticated)/tasks/page.test.tsx

@@ -4,7 +4,7 @@ import TasksPage from "./page";
 
 // Mock the TaskList component
 vi.mock("@/components/tasks/TaskList", () => ({
-  TaskList: ({ tasks, isLoading }: { tasks: unknown[]; isLoading: boolean }) => (
+  TaskList: ({ tasks, isLoading }: { tasks: unknown[]; isLoading: boolean }): React.JSX.Element => (
     <div data-testid="task-list">{isLoading ? "Loading" : `${String(tasks.length)} tasks`}</div>
   ),
 }));

apps/web/src/app/chat/page.tsx

@@ -28,19 +28,19 @@ export default function ChatPage(): ReactElement {
   const [sidebarOpen, setSidebarOpen] = useState(false);
   const [currentConversationId, setCurrentConversationId] = useState<string | null>(null);
 
-  const handleConversationChange = (conversationId: string | null) => {
+  const handleConversationChange = (conversationId: string | null): void => {
     setCurrentConversationId(conversationId);
     // NOTE: Update sidebar when conversation changes (see issue #TBD)
   };
 
-  const handleSelectConversation = async (conversationId: string | null) => {
+  const handleSelectConversation = async (conversationId: string | null): Promise<void> => {
     if (conversationId) {
       await chatRef.current?.loadConversation(conversationId);
       setCurrentConversationId(conversationId);
     }
   };
 
-  const handleNewConversation = (projectId?: string | null) => {
+  const handleNewConversation = (projectId?: string | null): void => {
     chatRef.current?.startNewConversation(projectId);
     setCurrentConversationId(null);
   };

apps/web/src/app/demo/kanban/page.tsx

@@ -157,7 +157,7 @@ const initialTasks: Task[] = [
 export default function KanbanDemoPage(): ReactElement {
   const [tasks, setTasks] = useState<Task[]>(initialTasks);
 
-  const handleStatusChange = (taskId: string, newStatus: TaskStatus) => {
+  const handleStatusChange = (taskId: string, newStatus: TaskStatus): void => {
     setTasks((prevTasks) =>
       prevTasks.map((task) =>
         task.id === taskId

apps/web/src/app/page.test.tsx

@@ -5,7 +5,11 @@ import Home from "./page";
 // Mock Next.js navigation
 const mockPush = vi.fn();
 vi.mock("next/navigation", () => ({
-  useRouter: () => ({
+  useRouter: (): {
+    push: typeof mockPush;
+    replace: ReturnType<typeof vi.fn>;
+    prefetch: ReturnType<typeof vi.fn>;
+  } => ({
     push: mockPush,
     replace: vi.fn(),
     prefetch: vi.fn(),
@@ -14,7 +18,13 @@ vi.mock("next/navigation", () => ({
 
 // Mock auth context
 vi.mock("@/lib/auth/auth-context", () => ({
-  useAuth: () => ({
+  useAuth: (): {
+    user: null;
+    isLoading: boolean;
+    isAuthenticated: boolean;
+    signOut: ReturnType<typeof vi.fn>;
+    refreshSession: ReturnType<typeof vi.fn>;
+  } => ({
     user: null,
     isLoading: false,
     isAuthenticated: false,

apps/web/src/app/settings/workspaces/[id]/teams/[teamId]/page.tsx

@@ -52,34 +52,38 @@ export default function TeamDetailPage(): ReactElement {
   const [team] = useState(mockTeamWithMembers);
   const [isLoading] = useState(false);
 
-  const handleUpdateTeam = async (data: { name?: string; description?: string }): Promise<void> => {
+  const handleUpdateTeam = (data: { name?: string; description?: string }): Promise<void> => {
     // TODO: Replace with real API call
     // await updateTeam(workspaceId, teamId, data);
     console.log("Updating team:", data);
     // TODO: Refetch team data
+    return Promise.resolve();
   };
 
-  const handleDeleteTeam = async (): Promise<void> => {
+  const handleDeleteTeam = (): Promise<void> => {
     // TODO: Replace with real API call
     // await deleteTeam(workspaceId, teamId);
     console.log("Deleting team");
 
     // Navigate back to teams list
     router.push(`/settings/workspaces/${workspaceId}/teams`);
+    return Promise.resolve();
   };
 
-  const handleAddMember = async (userId: string, role?: TeamMemberRole): Promise<void> => {
+  const handleAddMember = (userId: string, role?: TeamMemberRole): Promise<void> => {
     // TODO: Replace with real API call
     // await addTeamMember(workspaceId, teamId, { userId, role });
     console.log("Adding member:", { userId, role });
     // TODO: Refetch team data
+    return Promise.resolve();
   };
 
-  const handleRemoveMember = async (userId: string): Promise<void> => {
+  const handleRemoveMember = (userId: string): Promise<void> => {
     // TODO: Replace with real API call
     // await removeTeamMember(workspaceId, teamId, userId);
     console.log("Removing member:", userId);
     // TODO: Refetch team data
+    return Promise.resolve();
   };
 
   if (isLoading) {