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/pes.rs

@@ -107,20 +107,17 @@ impl PesFrame {
     /// truncated `.pes` data would be accepted as a graceful end.
     pub fn deserialize(r: &mut dyn std::io::Read) -> std::io::Result<Option<Self>> {
         // Probe one byte first to distinguish clean EOF from a truncated
-        // header.
+        // header. Loop on EINTR so back-to-back signals don't fail a
+        // recoverable read — symmetric with read_exact's internal retry
+        // on the rest of the header and the data below.
         let mut first = [0u8; 1];
-        match r.read(&mut first) {
-            Ok(0) => return Ok(None), // clean EOF, no frame started
-            Ok(_) => {}
-            Err(e) if e.kind() == std::io::ErrorKind::Interrupted => {
-                // Retry-once on EINTR before committing to the header read.
-                match r.read(&mut first) {
-                    Ok(0) => return Ok(None),
-                    Ok(_) => {}
-                    Err(e) => return Err(e),
-                }
+        loop {
+            match r.read(&mut first) {
+                Ok(0) => return Ok(None), // clean EOF, no frame started
+                Ok(_) => break,
+                Err(e) if e.kind() == std::io::ErrorKind::Interrupted => continue,
+                Err(e) => return Err(e),
             }
-            Err(e) => return Err(e),
         }
 
         let mut header = [0u8; 22]; // 1 + 8 + 1 + 8 + 4