fix: assorted correctness fixes and dead-code cleanup

- aacs/resolve: a media-keys-only provider missing the VID classifies as
  VidUnavailable, not NoMaterial (an MK derives the VUK once the VID
  arrives).
- disc/bluray: mark a clip seen only after its .clpi parses, so a
  transient parse failure on the first PlayItem cannot suppress the
  clip's extents for a later PlayItem referencing it that succeeds.
- disc/patch: log rather than swallow mapfile record/flush failures on a
  reverify downgrade, so a failed persist cannot silently mismark a bad
  unit good on resume.
- mux/ts: flag a discontinuity when a partial PES is dropped, matching
  the other partial-drop paths.
- mux/demux_thread: the no-demuxer branch forwards an empty batch for
  early consumer-disconnect detection instead of reading the whole disc.
- io/pipeline: correct the send-timing log (as_secs_f64, not as_micros
  printed as ms).
- aacs/derive, aacs/variant, disc/read_error, keysource: comment/doc
  accuracy. sector/prefetched, udf: remove dead fields/functions.
- mux/disc: assert unit-aligned read counts in the test.

src/udf.rs

@@ -325,53 +325,6 @@ impl UdfFs {
         Ok(merged)
     }
 
-    /// All sector ranges that contain data (metadata + all files including STREAM).
-    /// For full disc-to-ISO dumps — reads only allocated sectors, skips gaps.
-    pub fn all_sector_ranges(&self, reader: &mut dyn SectorSource) -> Result<Vec<(u32, u32)>> {
-        let mut ranges = Vec::new();
-
-        // UDF structure sectors
-        let meta_end = self.metadata_start.saturating_add(self.metadata_sectors);
-        ranges.push((0, meta_end));
-
-        // Walk entire tree including STREAM directories
-        self.collect_all_file_ranges(reader, &self.root, &mut ranges)?;
-
-        // Merge overlapping/adjacent ranges and sort
-        ranges.sort_by_key(|r| r.0);
-        let merged = merge_ranges(&ranges);
-        Ok(merged)
-    }
-
-    fn collect_all_file_ranges(
-        &self,
-        reader: &mut dyn SectorSource,
-        entry: &DirEntry,
-        ranges: &mut Vec<(u32, u32)>,
-    ) -> Result<()> {
-        for child in &entry.entries {
-            if child.is_dir {
-                self.collect_all_file_ranges(reader, child, ranges)?;
-            } else {
-                // Include the ICB sector
-                ranges.push((self.meta_to_abs(child.meta_lba)?, 1));
-
-                // Include ALL file data extents (large m2ts files have many)
-                if let Ok(extents) = self.read_icb_extents(reader, child.meta_lba) {
-                    for (data_lba, data_len) in extents {
-                        let abs_start = match self.partition_start.checked_add(data_lba) {
-                            Some(v) => v,
-                            None => continue,
-                        };
-                        let sector_count = (data_len as u64).div_ceil(2048) as u32;
-                        ranges.push((abs_start, sector_count));
-                    }
-                }
-            }
-        }
-        Ok(())
-    }
-
     fn collect_file_ranges(
         &self,
         reader: &mut dyn SectorSource,