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/css/stevenson.rs

@@ -402,7 +402,7 @@ mod tests {
 
     #[test]
     fn crack_unscrambled_returns_none() {
-        let sector = vec![0u8; 2048];
+        let sector = vec![0u8; SECTOR_BYTES];
         assert!(crack_title_key(&sector).is_none());
     }
 
@@ -414,7 +414,7 @@ mod tests {
 
     #[test]
     fn recover_needs_min_plain() {
-        let sector = vec![0u8; 2048];
+        let sector = vec![0u8; SECTOR_BYTES];
         let short_plain = [0u8; 4];
         assert!(recover_title_key(&sector, &short_plain).is_none());
     }