verify: post-read decrypt-verify gate + libaacs-strict verify + audit fixes

Post-read verify gate (new src/disc/verify.rs): UnitVerifier buffers/aligns the disc-absolute read stream into clip-file 6144-byte units, then makes one decryptability() decision per unit (CPI gate -> held keys -> key_fetch -> strict TS). POST_READ_VERIFY const kill-switch; fail-safe contract (only ever downgrades units it is confident are undecryptable; every doubt skips). Hooked into Disc::sweep (producer observes ciphertext -> WorkItem::MarkBad after the Good, FIFO-ordered) and Disc::patch (post-loop reverify_iso reads recovered units whole from the patched ISO). extract::clip_layouts enumerates AACS clips for the gate.

Standards-correct AACS verify: aacs::unit_is_clean_ts is a strict port of libaacs _verify_ts (all 32 TS syncs, not a majority vote); decrypt_unit accepts a key only on it; the majority verify_ts is removed. Deleted the Disc::verify_clips post-pass bolt-on (its primitive is absorbed by the read-path gate).

libaacs/DVD audit fixes: content-cert bus_encryption flag now read from bit 7 (was bit 0 - defeated the bus-key fail-loud gate); cc_id read from offset 14; title_cps_unit range-validated + 1->0 index-converted per libaacs. Corrected attack_crib ("functionally-equivalent" not "exact" port) and read_disc_key (READ DVD STRUCTURE 0xAD, not REPORT KEY) doc comments.

Also includes accumulated uncommitted work: key-fetch seam and TrueHD/DTS audio fix.

src/aacs/mod.rs

@@ -31,9 +31,10 @@ pub use trace::{KeyNode, KeyOutcome, KeyStep, ResolutionTrace, UnlockOutcome, Un
 // Explicit re-exports — only items needed by external consumers and sibling crate modules.
 // AES primitives (aes_ecb_encrypt, aes_ecb_decrypt, aes_cbc_decrypt) are pub(crate) in decrypt.rs.
 pub use decrypt::{
-    ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, UnitKeyResult, decrypt_bus, decrypt_unit,
-    decrypt_unit_full, decrypt_unit_try_keys, is_aacs_scrambled, is_unit_aligned, ts_packet_total,
-    ts_sync_count, unit_key_validates,
+    ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, UnitKeyResult, aacs_unit_encrypted,
+    aacs_unit_needs_decrypt, decrypt_bus, decrypt_unit, decrypt_unit_full, decrypt_unit_try_keys,
+    is_unit_aligned, ts_packet_total, ts_sync_count, ts_sync_destroyed, unit_is_clean_ts,
+    unit_key_validates,
 };
 // `probe` is a reproduction-harness helper (see keys.rs), not part of the
 // documented 1.0 surface; keep it reachable but off the rendered docs so we
@@ -97,7 +98,7 @@ mod tests {
         // Touch a representative function from each re-export group so a
         // dropped/renamed export fails to compile. These are smoke calls, not
         // behavioural assertions (behaviour is covered in each module).
-        let _ = is_aacs_scrambled(&[0u8; ALIGNED_UNIT_LEN]);
+        let _ = ts_sync_destroyed(&[0u8; ALIGNED_UNIT_LEN]);
         let _ = mkb_content_len(&[]);
         let _ = is_variant_mkb(&walk_mkb(&[]));
         let _ = disc_hash_hex(&disc_hash(b"x"));