1.1.1: unify AACS key-input path on Disc::inputs() + named constants

- read_aacs_inputs* now returns the AACS major version; DiscInputs carries it,
  and DiscInputsCtx parses Unit_Key_RO.inf at the disc's own stride (fixes the
  hardcoded-V20 read-time fetch for V10 discs). One source of truth, no version
  argument to drift.
- Disc::inputs() is the single complete AACS-input source (inf/MKB/VID/hash/
  version); the out-of-band duplicate readers go away.
- Named constants for AACS file paths (aacs::PATH_*) and the AACS majors
  (aacs::AACS_MAJOR_*, AacsVersion::major/from_major) replace magic strings/ints.
- push_ranges saturating (corrupt-disc panic guard).

src/aacs/keys.rs

@@ -24,6 +24,13 @@ pub enum AacsVersion {
     V21,
 }
 
+/// AACS major version as the small integer threaded through the scan / key
+/// paths (`AacsState.version`, `DiscInputs.version`, `DiscInputsCtx::new`):
+/// 1 = AACS 1.0 (BD), 2 = AACS 2.x (UHD). Centralised so the bare `1`/`2` — and
+/// the V10-vs-else stride choice it drives — lives in exactly one place.
+pub const AACS_MAJOR_BD: u8 = 1;
+pub const AACS_MAJOR_UHD: u8 = 2;
+
 impl AacsVersion {
     /// Stride (in bytes) between successive encrypted unit keys in
     /// `Unit_Key_RO.inf`.
@@ -33,6 +40,24 @@ impl AacsVersion {
             AacsVersion::V20 | AacsVersion::V21 => 64,
         }
     }
+
+    /// This version as the major integer ([`AACS_MAJOR_BD`] / [`AACS_MAJOR_UHD`]).
+    pub fn major(self) -> u8 {
+        match self {
+            AacsVersion::V10 => AACS_MAJOR_BD,
+            AacsVersion::V20 | AacsVersion::V21 => AACS_MAJOR_UHD,
+        }
+    }
+
+    /// The version a bare major integer selects for stride purposes: only the
+    /// BD major is V10; every other value takes the V20/V21 64-byte stride.
+    pub fn from_major(major: u8) -> Self {
+        if major == AACS_MAJOR_BD {
+            AacsVersion::V10
+        } else {
+            AacsVersion::V20
+        }
+    }
 }
 
 // ── VUK derivation ──────────────────────────────────────────────────────────

src/aacs/mod.rs

@@ -23,6 +23,18 @@ pub mod trace;
 pub mod types;
 pub mod variants;
 
+/// On-disc UDF paths to the AACS key-input files (with their fallbacks).
+/// Centralised so every reader (`resolve_vid_only`, `read_aacs_inputs`,
+/// `read_mkb_content`, `read_aacs_version`) walks the exact same files — adding
+/// or changing a fallback in one place can then never silently diverge the
+/// disc_hash / MKB / VID that another reader feeds a key service.
+pub const PATH_UNIT_KEY_RO: &str = "/AACS/Unit_Key_RO.inf";
+pub const PATH_UNIT_KEY_RO_DUPLICATE: &str = "/AACS/DUPLICATE/Unit_Key_RO.inf";
+pub const PATH_MKB_RO: &str = "/AACS/MKB_RO.inf";
+pub const PATH_MKB_RW: &str = "/AACS/MKB_RW.inf";
+pub const PATH_CONTENT_CERT: &str = "/AACS/Content000.cer";
+pub const PATH_CONTENT_CERT_ALT: &str = "/AACS/Content001.cer";
+
 // Boil-down derivation primitives (thin newtypes + wrappers over the crypto).
 pub use boil::{MediaKey, UnitKey, Vid, Vuk, mk_from_dk, mk_from_pk, uk_from_vuk, vuk_from_mk};
 // Structured, English-free resolution trace.
@@ -42,9 +54,9 @@ pub use decrypt::{
 #[doc(hidden)]
 pub use keys::probe;
 pub use keys::{
-    AacsVersion, ContentCert, MKB_20_CATEGORY_C, MKB_21_CATEGORY_C, MKB_TYPE_3_RECORDABLE,
-    MKB_TYPE_4_PRERECORDED, MKB_TYPE_10_CLASS_II, MkbType, ResolveContext, ResolveFailure,
-    ResolvedKeys, UnitKeyFile, decrypt_unit_key, derive_media_key_and_pk_from_dk,
+    AACS_MAJOR_BD, AACS_MAJOR_UHD, AacsVersion, ContentCert, MKB_20_CATEGORY_C, MKB_21_CATEGORY_C,
+    MKB_TYPE_3_RECORDABLE, MKB_TYPE_4_PRERECORDED, MKB_TYPE_10_CLASS_II, MkbType, ResolveContext,
+    ResolveFailure, ResolvedKeys, UnitKeyFile, decrypt_unit_key, derive_media_key_and_pk_from_dk,
     derive_media_key_from_dk, derive_media_key_from_pk, derive_vuk, disc_hash, disc_hash_hex,
     mkb_content_len, mkb_is_uhd, mkb_type, mkb_type_raw, mkb_version, parse_content_cert,
     parse_unit_key_ro, read_mkb_from_drive, recover_dk_position, resolve_keys_v1, resolve_keys_v2,