fix(watcher): fix TickCount wrap and resume retry on API failure

- Use 32-bit Environment.TickCount with unchecked uint arithmetic so
  GetIdleTime stays correct after the ~49.7 day uint wrap boundary
- Only clear _pausedTaskId after successful resume, not before the API call
- Add retry path: if resume failed, retry on next poll cycle while user
  is still active

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

WindowWatcher/NativeMethods.cs

@@ -29,6 +29,7 @@ internal static partial class NativeMethods
         var info = new LASTINPUTINFO { cbSize = (uint)Marshal.SizeOf<LASTINPUTINFO>() };
         if (!GetLastInputInfo(ref info))
             return TimeSpan.Zero;
-        return TimeSpan.FromMilliseconds(Environment.TickCount64 - info.dwTime);
+        // Use 32-bit TickCount so both values wrap at the same boundary as dwTime (uint)
+        return TimeSpan.FromMilliseconds(unchecked((uint)Environment.TickCount - info.dwTime));
     }
 }

WindowWatcher/Worker.cs

@@ -73,7 +73,12 @@ public class Worker(
 
                 // Idle detection
                 var idleTime = NativeMethods.GetIdleTime();
-                if (!_isIdle && idleTime.TotalMilliseconds >= config.IdleTimeoutMs)
+                if (!_isIdle && _pausedTaskId is not null && idleTime.TotalMilliseconds < config.IdleTimeoutMs)
+                {
+                    // Retry resume from a previous failed attempt
+                    await ResumeIdlePausedTaskAsync(ct: stoppingToken);
+                }
+                else if (!_isIdle && idleTime.TotalMilliseconds >= config.IdleTimeoutMs)
                 {
                     _isIdle = true;
                     logger.LogInformation("User idle for {IdleTime}, pausing active task", idleTime);
@@ -167,7 +172,6 @@ public class Worker(
             return;
 
         var taskId = _pausedTaskId.Value;
-        _pausedTaskId = null;
 
         try
         {
@@ -180,6 +184,7 @@ public class Worker(
             if (response?.Data is null || response.Data.Status != "Paused")
             {
                 logger.LogDebug("Task {TaskId} is no longer paused, skipping auto-resume", taskId);
+                _pausedTaskId = null;
                 return;
             }
 
@@ -189,13 +194,18 @@ public class Worker(
                 new { note = "Auto-resumed: user returned" }, ct);
 
             if (resumeResponse.IsSuccessStatusCode)
+            {
                 logger.LogInformation("Auto-resumed task {TaskId}", taskId);
+                _pausedTaskId = null;
+            }
             else
-                logger.LogWarning("Failed to resume task {TaskId}: {Status}", taskId, resumeResponse.StatusCode);
+            {
+                logger.LogWarning("Failed to resume task {TaskId}: {Status}, will retry", taskId, resumeResponse.StatusCode);
+            }
         }
         catch (Exception ex)
         {
-            logger.LogWarning(ex, "Failed to resume task {TaskId} after idle", taskId);
+            logger.LogWarning(ex, "Failed to resume task {TaskId} after idle, will retry", taskId);
         }
     }
 }