fix: SDSL cache double-check validation

The lazy inner double-check in ShaderLoaderBase.LoadExternalBuffer
skipped ValidateCachedHashes, so when the outer check detected a
source hash mismatch and fell through, the inner check would hit
the same (memory-cached) stale entry and return it unchanged. Now
the inner check also validates hashes.

Author: xen2

sources/shaders/Stride.Shaders.Compilers/ShaderLoaderBase.cs

@@ -60,7 +60,7 @@ public bool LoadExternalBuffer(string name, ReadOnlySpan<ShaderMacro> defines, [
         var lazy = compilingShaders.GetOrAdd(key, _ => new Lazy<(ShaderBuffers, ObjectId)>(() =>
         {
             // Double-check cache (another thread may have finished between our check and this factory)
-            if (Cache.TryLoadFromCache(name, null, macrosArray, out var buf, out var h))
+            if (Cache.TryLoadFromCache(name, null, macrosArray, out var buf, out var h) && ValidateCachedHashes(buf))
                 return (buf, h);
 
             if (!ExternalFileExists(name))