feat(assets): seven asset commands + Run dispatch/helpers

check-dupes, clean-dupes, check-mdl, fix-mdl, convert, upscale, compile
behind a single runner indirection, mirroring internal/depot's Run shape.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/assets/fixmdl_test.go

@@ -0,0 +1,48 @@
+package assets
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/assets/mdl"
+)
+
+func TestFixMDL(t *testing.T) {
+	dir := t.TempDir()
+	// Uppercase name + internal mismatch.
+	upper := filepath.Join(dir, "Foo.MDL")
+	body := "newmodel wrong\nbeginmodelgeom wrong\nendmodelgeom wrong\ndonemodel wrong\n"
+	if err := os.WriteFile(upper, []byte(body), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	// dry-run: nothing changes on disk.
+	var out, errw bytes.Buffer
+	if code := runFixMDL([]string{"--dry-run", dir}, &out, &errw); code != exitOK {
+		t.Fatalf("dry-run exit = %d\n%s", code, errw.String())
+	}
+	if _, err := os.Stat(upper); err != nil {
+		t.Fatal("dry-run renamed a file")
+	}
+
+	// real run: file is lowercased and its identity rewritten to match.
+	out.Reset()
+	errw.Reset()
+	if code := runFixMDL([]string{dir}, &out, &errw); code != exitOK {
+		t.Fatalf("fix exit = %d\n%s", code, errw.String())
+	}
+	lowered := filepath.Join(dir, "foo.mdl")
+	if _, err := os.Stat(lowered); err != nil {
+		t.Fatalf("file was not lowercased: %v", err)
+	}
+	mismatches, err := mdl.CheckNames(lowered)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(mismatches) != 0 {
+		data, _ := os.ReadFile(lowered)
+		t.Fatalf("model still has mismatches after fix: %+v\n%s", mismatches, data)
+	}
+}