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/lib.rs

@@ -87,6 +87,7 @@
 
 pub mod aacs;
 pub(crate) mod clpi;
+pub mod consts;
 pub mod css;
 pub mod decrypt;
 pub mod diag;
@@ -167,7 +168,7 @@ pub use identity::DriveId;
 // and registers it once at process start via `register_unlocker`. At
 // drive-prep the registry is walked in order; the first matching unlocker
 // runs, else the drive falls through to the host-cert AACS handshake.
-pub use unlock::{Unlocker, register_unlocker};
+pub use unlock::{UnlockError, Unlocker, register_unlocker};
 
 // ─── Decryption (AACS / CSS) ────────────────────────────────────────────────
 //