0.31.0: hardening and correctness pass across mux, codec, AACS/CSS, UDF/MPLS/CLPI, recovery, drive/SCSI, labels, and I/O

Library-wide review-and-fix pass: tightened AACS keydb/handshake/variant
handling and trailing-partial-unit policy, corrected MPLS mark offset and
added UDF allocation bounds, hardened the mux/codec framing and M2TS paths,
guarded SCSI READ CAPACITY short transfers and unified error mapping, added
overflow guards on untrusted disc input, and made prefetch shutdown
deterministic. Release profile now builds with thin LTO + single codegen unit.

src/sector/decrypting.rs

@@ -1,12 +1,12 @@
 //! `DecryptingSectorSource` — wrap any [`SectorSource`] to apply
 //! AACS / CSS in-place decryption on every read.
 //!
-//! This is the 0.18 single-source-of-truth for decrypt-on-read. The
-//! actual cipher code lives in [`crate::aacs`] and [`crate::css`];
-//! we just call the existing [`crate::decrypt::decrypt_sectors`]
-//! helper that already drives both of them. In follow-up commits
-//! `sweep_pipeline` and `DiscStream` migrate onto this decorator
-//! and delete their duplicate decrypt call sites.
+//! This is the single source of truth for decrypt-on-read: every
+//! decrypt-on-read caller (e.g. `DiscStream`) wraps its source in this
+//! decorator. The actual cipher code lives in [`crate::aacs`] and
+//! [`crate::css`]; we just call the existing
+//! [`crate::decrypt::decrypt_sectors`] helper that drives both of them
+//! in-place after each read (a no-op for [`DecryptKeys::None`]).
 //!
 //! Composition: `Drive` → `DecryptingSectorSource` → caller sees
 //! plaintext. For `DecryptKeys::None` discs the decorator is a
@@ -94,10 +94,8 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
         recovery: bool,
     ) -> Result<usize> {
         let n = self.inner.read_sectors(lba, count, buf, recovery)?;
-        // Reuse the existing crate-wide decrypt entry point — same
-        // path the 0.17 sweep_pipeline and DiscStream call, so we
-        // inherit their AACS / CSS / None semantics verbatim. The
-        // helper is a no-op for DecryptKeys::None.
+        // Apply the crate-wide AACS/CSS/None decrypt entry point in-place
+        // over the bytes just read. No-op for DecryptKeys::None.
         decrypt_sectors(&mut buf[..n], &self.keys, self.unit_key_idx)?;
         Ok(n)
     }