DVD vob_start absolute rebase + rc.5.3 audit fixes

- ifo.rs: rebase VTS title VOBS to absolute disc LBA (file_start_lba +
  vtstt_vobs); fixes DVD rips opening on the menu region instead of the
  movie (e.g. SOTL). Adds absolute-placement regression test.
- aacs/boil.rs: add mk_from_pk primitive (PK -> MK via MKB walk).
- dvdnav/: nav-VM command decoder + start-cell resolver seam, parked
  behind USE_NAV_RESOLVER (kept compiled, never executed).
- mux: FVI src.byte within-sector per spec; Unknown colour -> CICP
  unspecified (2,2,2,1); demux clear PCS -> NORMAL; ts.rs feed() base
  reset + boundary provenance fix.
- Assorted audit fixes (doc/comment/test accuracy) across the crate.

src/drive/mod.rs

@@ -433,8 +433,12 @@ impl Drive {
                 }
                 Ok(())
             }
-            // No unlocker matched: not an error — fall through to OEM route.
+            // No unlocker matched, or one matched but only hit a capability
+            // failure (not firmware-unlockable / no OEM VID): not an error —
+            // fall through to the OEM host-cert route.
             Ok(None) => Ok(()),
+            // A genuine transport fault during unlock (UnlockError::Scsi)
+            // propagates here and aborts init — the bus is dead.
             Err(e) => Err(e),
         };
         tracing::info!(