test: assert full key bytes; correct keydb-format docs

Several tests asserted only key[0] (the first byte), which a byte-transposition bug could pass — assert the full 16-byte key everywhere, including a KAT that recomputes the expected VUK-derived keys directly. test_parse_disc_entry used identical all-zero placeholders for M/I/V/U, which couldn't catch a field mix-up; give each field a distinct byte pattern and assert every field.

Docs: keydb-format.md claimed DiscEntry::title was genuinely unused dead code, but it's read by to_keydb_cfg and the redacting Debug impl — correct the comment to only list empty/find_vuk as truly unused. Also cross-reference the two independent MAX_KEYDB_BYTES constants (keydb.rs's decompression cap and keydb_format.rs's on-disk load cap) so they're kept in sync, and bump Cargo.lock's version metadata.

docs/keydb-format.md

@@ -10,10 +10,12 @@ revision of this comment cited a `candidates_from` function — no such
 function has ever existed in this crate; the real consumer is
 `KeydbSource::unit_keys_from` (keydb.rs), which reads `unit_keys`, `vuk`,
 `media_key` AND `vid` (`vid` is load-bearing for the MK+VID derivation the
-kat_c / kat_d KATs pin — it is NOT unused). The genuinely unused items —
-`empty`, `find_vuk`, `DiscEntry::title` — are part of the faithful copy and
-are retained rather than pruned; allow dead_code so the byte-for-byte copy
-compiles clean without diverging from the libfreemkv original.
+kat_c / kat_d KATs pin — it is NOT unused). `DiscEntry::title` is likewise
+read — by `to_keydb_cfg` and the redacting `Debug` impl — so it is not
+unused either. The genuinely unused items — `empty` and `find_vuk` — are
+part of the faithful copy and are retained rather than pruned; allow
+dead_code so the byte-for-byte copy compiles clean without diverging from
+the libfreemkv original.
 
 ## ParseStats — what `KeyDb::parse` threw away