1.2.0: mux loss-concealment read path (P3/Edit-2, A2 NULL-TS fill)

Decrypt-verify is a RIP gate, not a MUX gate. On the mux read path an
undecryptable content unit must never abort the mux:

- DecryptingSectorSource gains tolerate_decrypt_loss(): when set, an
  undecryptable in-content unit is tallied, overwritten with valid NULL
  TS packets (PID 0x1FFF) via aacs::fill_null_ts_unit, logged loud with
  its LBA, and the read returns Ok — the stream keeps flowing. The rip
  paths keep the fail-loud DECRYPT_VERIFY_READ decorator (re-read off the
  disc); only the mux opts in.
- Wire it into both mux read paths: the file-backed highway
  (build_iso_pipeline) and the inline DiscStream.
- NULL-TS fill keeps the demuxer byte-synced on the 192-byte stride; the
  lost video/audio PID packets surface as a CC gap the TS assembler
  already drops a partial PES on (the B1 foundation). Ciphertext is never
  passed downstream either way.
- Fix stale resolve_vid_only no-cert test: default is UHD (audit #4).

Tests: conceal-as-NULL-TS, fill well-formedness, fail-loud still holds.

src/mux/disc.rs

@@ -227,7 +227,12 @@ impl DiscStream {
 
         // CSS/unencrypted content needs a decrypting wrapper to yield plaintext
         // VOB bytes before the AC-3 sub-stream probe can read real `acmod`s.
-        let mut reader = DecryptingSectorSource::new(reader, decrypt_keys.clone());
+        // MUX path: tolerate decrypt loss — conceal an undecryptable unit (NULL TS
+        // fill) + tally + log rather than abort the stream (P3). DiscStream is a
+        // decode/mux stream (live-drive single-pass / direct), never the
+        // ciphertext-preserving sweep, so concealment is always correct here.
+        let mut reader =
+            DecryptingSectorSource::new(reader, decrypt_keys.clone()).tolerate_decrypt_loss();
 
         // Wrong-substream fix (Silence-of-the-Lambs): re-route the title's
         // declared AC-3 audio onto the physically-correct `0x8x` sub-streams by