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/labels/mod.rs

@@ -1124,9 +1124,10 @@ mod registry_tests {
             // and as a marker for "these parsers exist."
             let _ = (name, detect, parse);
         }
-        // The loop above touches every registry entry; iterating a non-empty
-        // fixed-size array is the assertion (a `.is_empty()` check would be
-        // const-folded). The test fails to compile if the tuple shape changes.
+        // The loop above touches every registry entry. The non-empty
+        // invariant is covered separately by `parsers_registry_order_locked`,
+        // whose assert_eq! on the expected order fails if PARSERS is empty.
+        // This test fails to compile if the tuple shape changes.
     }
 }