unlock/patch: preserve SCSI sense across the bridge; init aborts on dead bus; slow-retry first patch failure

Audit fixes (v1.1.0..HEAD regressions in the unlock migration + adaptive patch
speed):

- unlock_bridge ScsiAdapter: libfreemkv's transport returns Err on ANY non-zero
  SCSI status (a normal CHECK CONDITION), not only transport faults. The adapter
  was collapsing every such Err to { status: 0xFF, sense: None }, which discarded
  the parsed sense and defeated the AACS handshake's ILLEGAL_REQUEST wedge guard
  (so it kept hammering the drive — hard-rule #2) and inverted its
  transport-vs-rejection diagnosis. Now reconstruct status + the 32-byte sense
  buffer (sense_key@2, asc@12, ascq@13) and only emit 0xFF/None for a genuine
  transport fault.

- Drive::init: a genuine transport fault during the drive-prep unlock means the
  bus is dead — propagate it (the v1.1.0 invariant) instead of silently
  swallowing it via `if let Ok`. Other errors (no matching unlocker) still fall
  through to stock mode. SET CD SPEED max now runs only when the bus is alive.

- disc::patch: on the first read failure in a range, drop to slow recovery speed
  and RE-ATTEMPT the same position at slow speed before marking it. A
  single-sector range's first failing sector was being marked from a MAX-speed
  read it never got to recover.

- docs: lib.rs architecture diagram (handshake → host_certs) and README (stale
  pluggable-unlock-seam / register-unlocker / crates.io / docs.rs references).

src/lib.rs

@@ -58,7 +58,7 @@
 //!   ├── JAR parser       -- BD-J audio track labels
 //!   └── AACS             -- encryption: key resolution + content decrypt
 //!       ├── aacs         -- KEYDB, VUK, MKB, unit decrypt
-//!       └── handshake    -- SCSI auth, ECDH, bus key
+//!       └── host_certs   -- collect host certs (cert handshake lives in freemkv-unlock)
 //! ```
 //!
 //! # AACS Encryption