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/io/pipeline.rs

@@ -449,7 +449,10 @@ impl<I: Send + 'static, R: Send + 'static> Pipeline<I, R> {
                     } else {
                         // Benign per-item OK: trace-level (L4) only; the
                         // apply-side rolling summary carries throughput.
-                        tracing::trace!("Pipeline send: OK in {:.3}ms", elapsed.as_micros());
+                        tracing::trace!(
+                            "Pipeline send: OK in {:.3}ms",
+                            elapsed.as_secs_f64() * 1000.0
+                        );
                     }
                 }
                 Ok(())
@@ -464,7 +467,10 @@ impl<I: Send + 'static, R: Send + 'static> Pipeline<I, R> {
                             std::any::type_name::<I>()
                         );
                     } else {
-                        tracing::debug!("Pipeline send: failed after {:.3}ms", elapsed.as_micros());
+                        tracing::debug!(
+                            "Pipeline send: failed after {:.3}ms",
+                            elapsed.as_secs_f64() * 1000.0
+                        );
                     }
                 }
                 Err(e.0)