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/sector/mod.rs

@@ -150,14 +150,11 @@ mod tests {
         speeds: Arc<Mutex<Vec<u16>>>,
     }
 
+    /// A `Spy` under test plus the handles recording its reads and speed sets.
+    type SpyHarness = (Spy, Arc<Mutex<Vec<(u32, u16, bool)>>>, Arc<Mutex<Vec<u16>>>);
+
     impl Spy {
-        fn new(
-            capacity: u32,
-        ) -> (
-            Self,
-            Arc<Mutex<Vec<(u32, u16, bool)>>>,
-            Arc<Mutex<Vec<u16>>>,
-        ) {
+        fn new(capacity: u32) -> SpyHarness {
             let reads = Arc::new(Mutex::new(Vec::new()));
             let speeds = Arc::new(Mutex::new(Vec::new()));
             (

src/sector/prefetched.rs

@@ -667,7 +667,7 @@ mod tests {
         assert!(err.is_err(), "zero batch_sectors must be rejected");
     }
 
-    /// >3 sequential direct `read_sectors` calls must succeed. The
+    /// More than 3 sequential direct `read_sectors` calls must succeed. The
     /// recycle pool seeds PREFETCH_CHANNEL_DEPTH+1 (3) buffers; before
     /// the fix the direct path dropped each drained buffer, so the 4th
     /// call deadlocked. Watchdog-guarded.