CSS crypto tests + DVD pipeline fully wired

- CSS roundtrip tests: decrypt_key determinism, descramble XOR roundtrip
- CSS table verification: TAB1 is permutation, TAB4 is bit-reversal involution
- DVD scan pipeline confirmed: scan_dvd_titles, CSS crack, ContentReader descramble
- 229 tests, all passing

src/mux/meta.rs

@@ -180,6 +180,7 @@ impl M2tsMeta {
             clips: Vec::new(),
             streams,
             extents: Vec::new(),
+            content_format: crate::disc::ContentFormat::BdTs,
         }
     }
 }