fix: Avoid stale var cache and poll for userspace

Force direct device queries and clear cached fastboot vars to avoid stale values after reboot/mode changes. IsUserspace() now calls GetVar(..., useCache:false). After rebooting to fastboot, _varCache is cleared before reconnect to ensure fresh vars. Reboot-to-userspace now polls up to 30s (1s intervals) for the device to report userspace, throwing an error if it doesn't appear, and preserves the existing small delay to match AOSP behavior.

Author: 13584452567

FirmwareKit.Comm.Fastboot/FastbootDriver.cs

@@ -39,7 +39,8 @@ public bool IsUserspace()
         FastbootDebug.Log($"IsUserspace()");
         try
         {
-            return GetVar("is-userspace") == "yes";
+            // Always query device directly; cached values can be stale across reboot mode changes.
+            return GetVar("is-userspace", useCache: false) == "yes";
         }
         catch
         {
@@ -343,6 +344,9 @@ public void EnsureUserspace()
             NotifyCurrentStep("Operation requires fastbootd, rebooting...");
             Reboot("fastboot").ThrowIfError();
 
+            // Clear stale vars (including is-userspace=no) before reconnect and re-check.
+            _varCache.Clear();
+
             // Match AOSP behavior: allow disconnect to happen before attempting reconnect.
             System.Threading.Thread.Sleep(1000);
             NotifyCurrentStep("waiting for any device >");
@@ -399,7 +403,20 @@ public void EnsureUserspace()
                 throw new NotSupportedException("Automatic reboot to userspace is only supported for USB, TCP and UDP transports.");
             }
 
-            if (!IsUserspace())
+            DateTime userspaceWaitStart = DateTime.Now;
+            bool enteredUserspace = false;
+            while ((DateTime.Now - userspaceWaitStart).TotalSeconds < 30)
+            {
+                if (IsUserspace())
+                {
+                    enteredUserspace = true;
+                    break;
+                }
+
+                System.Threading.Thread.Sleep(1000);
+            }
+
+            if (!enteredUserspace)
             {
                 throw new Exception("Failed to boot into userspace fastboot; one or more components might be unbootable.");
             }