Tool: Polish Pass 1

In sow-tools, extract now behaves like a real sync by default: it
overwrites changed extracted files, removes stale extracted files that
no longer exist in the built archives, and normalizes extracted resource
filenames to lowercase. I also made validation warn on uppercase
resource filenames so mixed-case names like I_ELVENCHAIN are surfaced
instead of quietly lingering. The extract command output now includes
overwritten and removed counts too.

internal/validator/validator_test.go

@@ -54,6 +54,49 @@ func TestValidateProjectWarnsForCrossHAKDuplicateAssets(t *testing.T) {
 	}
 }
 
+func TestValidateProjectWarnsForUppercaseResourceNames(t *testing.T) {
+	root := t.TempDir()
+	mustMkdir(t, filepath.Join(root, "src", "blueprints", "items"))
+	mustMkdir(t, filepath.Join(root, "assets", "vfx"))
+	mustMkdir(t, filepath.Join(root, "build"))
+
+	mustWriteFile(t, filepath.Join(root, "nwn-tool.json"), `{
+  "module": {
+    "name": "Test Module",
+    "resref": "testmod"
+  },
+  "paths": {
+    "source": "src",
+    "assets": "assets",
+    "build": "build"
+  }
+}
+`)
+	mustWriteFile(t, filepath.Join(root, "src", "blueprints", "items", "I_ELVENCHAIN.uti.json"), `{
+  "file_type": "UTI ",
+  "file_version": "V3.2",
+  "root": {"struct_type": 0, "fields": []}
+}
+`)
+	mustWriteFile(t, filepath.Join(root, "assets", "vfx", "SPELL_FIRE.tga"), "fire")
+
+	p, err := project.Load(root)
+	if err != nil {
+		t.Fatalf("load project: %v", err)
+	}
+	if err := p.ValidateLayout(); err != nil {
+		t.Fatalf("validate layout: %v", err)
+	}
+	if err := p.Scan(); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+
+	report := ValidateProject(p)
+	if report.WarningCount() < 2 {
+		t.Fatalf("expected lowercase warnings, got %#v", report.Diagnostics)
+	}
+}
+
 func mustMkdir(t *testing.T, path string) {
 	t.Helper()
 	if err := os.MkdirAll(path, 0o755); err != nil {