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/mux/m2ts_mux/mod.rs

@@ -254,7 +254,10 @@ impl<W: Write> M2tsMux<W> {
         // step — e.g. a leading audio frame ahead of the first video keyframe),
         // which still floors to 0 per the documented behavior.
         let delta = raw_90k.wrapping_sub(base) & 0x1_FFFF_FFFF;
-        if delta > (1 << 32) { 0 } else { delta }
+        // Signed 33-bit: the sign bit is bit 32 (value 2^32), so the entire
+        // upper half [2^32, 2^33) is negative (frame before base) and floors
+        // to 0. delta == 2^32 is the most-negative value (-2^32), hence `>=`.
+        if delta >= (1 << 32) { 0 } else { delta }
     }
 
     /// Emit one PES payload as a chain of TS packets on `pid`. If `pcr`