verify: container-kind seam (HD-DVD-ready) + skip units with unread sectors

ContainerKind {Ts,Ps} + ClipLayout.container thread the post-decrypt structural check per clip; decryptability() dispatches it (TS: unit_is_clean_ts, PS: unit_is_clean_ps). New decrypt_unit_checked(unit,key,accept) decouples the container-agnostic AACS crypto from the format-specific acceptance (decrypt_unit delegates with the TS check). unit_is_clean_ps is the MPEG-2 PS pack-start check, documented UNVALIDATED for HD-DVD (.evo unit/seed/pack alignment must be confirmed on real media). clip_layouts assigns Ts today; .evo->Ps is the one-line HD-DVD hook.

reverify_iso now takes an is_finished predicate and SKIPS any unit with a non-Finished backing sector: we can't verify what wasn't read (a non-Finished sector is zero-filled because the drive read failed there), and must never waste a key lookup on a block the read already knows is bad. observe() (sweep) was already safe (only fed Good bytes).

src/aacs/mod.rs

@@ -33,8 +33,8 @@ pub use trace::{KeyNode, KeyOutcome, KeyStep, ResolutionTrace, UnlockOutcome, Un
 pub use decrypt::{
     ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, UnitKeyResult, aacs_unit_encrypted,
     aacs_unit_needs_decrypt, decrypt_bus, decrypt_unit, decrypt_unit_full, decrypt_unit_try_keys,
-    is_unit_aligned, ts_packet_total, ts_sync_count, ts_sync_destroyed, unit_is_clean_ts,
-    unit_key_validates,
+    decrypt_unit_checked, is_unit_aligned, ts_packet_total, ts_sync_count, ts_sync_destroyed,
+    unit_is_clean_ps, unit_is_clean_ts, unit_key_validates,
 };
 // `probe` is a reproduction-harness helper (see keys.rs), not part of the
 // documented 1.0 surface; keep it reachable but off the rendered docs so we