feat: added Files app USB medium detection

kernel/src/Fs/FsProbe.cpp

@@ -142,6 +142,18 @@ namespace Fs::FsProbe {
         return -1;
     }
 
+    int GetBlockDeviceForDrive(int driveNum) {
+        if (driveNum < 0) return -1;
+        int partCount = Drivers::Storage::Gpt::GetPartitionCount();
+        for (int i = 0; i < partCount && i < Drivers::Storage::Gpt::MaxPartitions; i++) {
+            if (g_mounted[i] && g_driveForPart[i] == driveNum) {
+                auto* part = Drivers::Storage::Gpt::GetPartition(i);
+                if (part) return part->BlockDevIndex;
+            }
+        }
+        return -1;
+    }
+
     int UnmountPartitionsForBlockDevice(int blockDevIndex) {
         int partCount = Drivers::Storage::Gpt::GetPartitionCount();
         int unmounted = 0;

kernel/src/Fs/FsProbe.hpp

@@ -34,4 +34,8 @@ namespace Fs::FsProbe {
     // mount bookkeeping to match Gpt::RemovePartitionsForBlockDevice().
     int UnmountPartitionsForBlockDevice(int blockDevIndex);
 
+    // Return the block-device index backing a mounted VFS drive, or -1 if the
+    // drive isn't backed by a partition (e.g. ramdisk).
+    int GetBlockDeviceForDrive(int driveNum);
+
 };