remove user-facing English from the library (KeyOrigin::name, hddvd Title)

Library holds ZERO user-facing English (CLAUDE.md). Removed KeyOrigin::name()'s
English prose — apps map the typed enum (freemkv gets key_origin_label); diag
logs the enum's Debug repr. hddvd unnamed-title fallback 'Title N' -> neutral
TITLE_N identifier (UDF volume-label style).

src/diag.rs

@@ -530,7 +530,7 @@ fn dump_aacs(disc: &Disc) {
         a.bus_encryption,
         a.mkb_version,
         a.disc_hash,
-        a.key_source.name(),
+        a.key_source,
         a.vuk.is_some(),
         a.unit_keys.len(),
         a.uk_ro.len(),