AACS pipeline reshape + TrueHD metadata + central consts + clippy/fmt clean

- AACS: delete in-lib keydb parser (Step 3); boil-down primitives
  (mk_from_dk/vuk_from_mk/uk_from_vuk) + newtypes; KeySource->get_uk(ctx)+
  ResolveCtx; Unlocker->unlock()->Result<Vid,UnlockError> + AacsCertUnlocker;
  OEM bus-key gate (AacsBusKeyUnavailable); structured ResolutionTrace (Step 4).
- TrueHD: sample-rate from major-sync, Atmos label, 44.1k AU duration.
- consts: central media/format constants module; 17 duplicate const-defs
  centralized (sector/TS-packet/source-packet); mpls stream-entry + category
  codes named.
- clippy --all-targets -D warnings clean (1.86); fmt clean; 2199 lib tests.

src/labels/bdmt.rs

@@ -385,7 +385,7 @@ mod tests {
             meta.titles.get("fra").map(String::as_str),
             Some("Aurora Drift (Partie Deux)")
         );
-        assert!(meta.descriptions.get("eng").is_none());
+        assert!(!meta.descriptions.contains_key("eng"));
         assert_eq!(
             meta.descriptions.get("fra").map(String::as_str),
             Some("Suite du film fictif.")