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/components/gantt/GanttChart.test.tsx

@@ -9,7 +9,7 @@ describe("GanttChart", (): void => {
   const baseDate = new Date("2026-02-01T00:00:00Z");
 
   const createGanttTask = (overrides: Partial<GanttTask> = {}): GanttTask => ({
-    id: `task-${Math.random()}`,
+    id: `task-${String(Math.random())}`,
     workspaceId: "workspace-1",
     title: "Sample Task",
     description: null,
@@ -90,7 +90,8 @@ describe("GanttChart", (): void => {
 
       render(<GanttChart tasks={tasks} />);
 
-      const taskRow = screen.getAllByText("Completed Task")[0]!.closest("[role='row']");
+      const taskElements = screen.getAllByText("Completed Task");
+      const taskRow = taskElements[0]?.closest("[role='row']");
       expect(taskRow?.className).toMatch(/Completed/i);
     });
 
@@ -105,7 +106,8 @@ describe("GanttChart", (): void => {
 
       render(<GanttChart tasks={tasks} />);
 
-      const taskRow = screen.getAllByText("Active Task")[0]!.closest("[role='row']");
+      const taskElements = screen.getAllByText("Active Task");
+      const taskRow = taskElements[0]?.closest("[role='row']");
       expect(taskRow?.className).toMatch(/InProgress/i);
     });
   });
@@ -219,8 +221,8 @@ describe("GanttChart", (): void => {
       expect(bars).toHaveLength(2);
 
       // Second bar should be wider (more days)
-      const bar1Width = bars[0]!.style.width;
-      const bar2Width = bars[1]!.style.width;
+      const bar1Width = bars[0]?.style.width;
+      const bar2Width = bars[1]?.style.width;
 
       // Basic check that widths are set (exact values depend on implementation)
       expect(bar1Width).toBeTruthy();
@@ -344,11 +346,15 @@ describe("GanttChart", (): void => {
 
       render(<GanttChart tasks={tasks} />);
 
-      const taskNames = screen.getAllByRole("row").map((row) => row.textContent);
+      const taskNames = screen.getAllByRole("row").map((row): string | null => row.textContent);
 
       // Early Task should appear first
-      const earlyIndex = taskNames.findIndex((name) => name?.includes("Early Task"));
-      const lateIndex = taskNames.findIndex((name) => name?.includes("Late Task"));
+      const earlyIndex = taskNames.findIndex(
+        (name): boolean => name?.includes("Early Task") ?? false
+      );
+      const lateIndex = taskNames.findIndex(
+        (name): boolean => name?.includes("Late Task") ?? false
+      );
 
       expect(earlyIndex).toBeLessThan(lateIndex);
     });

apps/web/src/components/gantt/GanttChart.tsx

@@ -34,10 +34,22 @@ function calculateTimelineRange(tasks: GanttTask[]): TimelineRange {
     };
   }
 
-  let earliest = tasks[0]!.startDate;
-  let latest = tasks[0]!.endDate;
+  const firstTask = tasks[0];
+  if (!firstTask) {
+    // This should not happen due to the check above, but makes TS happy
+    const now = new Date();
+    const oneMonthLater = new Date(now.getTime() + 30 * 24 * 60 * 60 * 1000);
+    return {
+      start: now,
+      end: oneMonthLater,
+      totalDays: 30,
+    };
+  }
 
-  tasks.forEach((task) => {
+  let earliest = firstTask.startDate;
+  let latest = firstTask.endDate;
+
+  tasks.forEach((task): void => {
     if (task.startDate < earliest) {
       earliest = task.startDate;
     }
@@ -82,8 +94,8 @@ function calculateBarPosition(
   const widthPercent = (taskDuration / totalDays) * 100;
 
   const result: GanttBarPosition = {
-    left: `${leftPercent}%`,
-    width: `${widthPercent}%`,
+    left: `${String(leftPercent)}%`,
+    width: `${String(widthPercent)}%`,
     top: rowIndex * 48, // 48px row height
   };
 
@@ -114,11 +126,11 @@ function getStatusClass(status: TaskStatus): string {
 function getRowStatusClass(status: TaskStatus): string {
   switch (status) {
     case TaskStatus.COMPLETED:
-      return styles.rowCompleted || "";
+      return styles.rowCompleted ?? "";
     case TaskStatus.IN_PROGRESS:
-      return styles.rowInProgress || "";
+      return styles.rowInProgress ?? "";
     case TaskStatus.PAUSED:
-      return styles.rowPaused || "";
+      return styles.rowPaused ?? "";
     default:
       return "";
   }
@@ -172,13 +184,16 @@ function calculateDependencyLines(
       return;
     }
 
-    task.dependencies.forEach((depId) => {
+    task.dependencies.forEach((depId): void => {
       const fromIndex = taskIndexMap.get(depId);
       if (fromIndex === undefined) {
         return;
       }
 
-      const fromTask = tasks[fromIndex]!;
+      const fromTask = tasks[fromIndex];
+      if (!fromTask) {
+        return;
+      }
 
       // Calculate positions (as percentages)
       const fromEndOffset = Math.max(

apps/web/src/components/gantt/types.test.ts

@@ -201,8 +201,8 @@ describe("Gantt Types Helpers", (): void => {
       const ganttTasks = toGanttTasks(tasks);
 
       expect(ganttTasks).toHaveLength(2);
-      expect(ganttTasks[0]!.id).toBe("task-1");
-      expect(ganttTasks[1]!.id).toBe("task-2");
+      expect(ganttTasks[0]?.id).toBe("task-1");
+      expect(ganttTasks[1]?.id).toBe("task-2");
     });
 
     it("should filter out tasks that cannot be converted", (): void => {
@@ -240,9 +240,9 @@ describe("Gantt Types Helpers", (): void => {
 
       const ganttTasks = toGanttTasks(tasks);
 
-      expect(ganttTasks[0]!.id).toBe("first");
-      expect(ganttTasks[1]!.id).toBe("second");
-      expect(ganttTasks[2]!.id).toBe("third");
+      expect(ganttTasks[0]?.id).toBe("first");
+      expect(ganttTasks[1]?.id).toBe("second");
+      expect(ganttTasks[2]?.id).toBe("third");
     });
   });
 });

apps/web/src/components/gantt/types.ts

@@ -78,25 +78,20 @@ function isStringArray(value: unknown): value is string[] {
  */
 export function toGanttTask(task: Task): GanttTask | null {
   // For Gantt chart, we need both start and end dates
-  const metadataStartDate = task.metadata?.startDate;
+  const metadataStartDate = task.metadata.startDate;
   const startDate = isDateString(metadataStartDate) ? new Date(metadataStartDate) : task.createdAt;
 
   const endDate = task.dueDate ?? new Date();
 
-  // Validate dates
-  if (!startDate || !endDate) {
-    return null;
-  }
-
   // Extract dependencies with type guard
-  const metadataDependencies = task.metadata?.dependencies;
+  const metadataDependencies = task.metadata.dependencies;
   const dependencies = isStringArray(metadataDependencies) ? metadataDependencies : undefined;
 
   const ganttTask: GanttTask = {
     ...task,
     startDate,
     endDate,
-    isMilestone: task.metadata?.isMilestone === true,
+    isMilestone: task.metadata.isMilestone === true,
   };
 
   if (dependencies) {