binary(tests): vector cases for zero code chunks in the code zone

tests/binary_trie/vectors/README.md

@@ -183,7 +183,7 @@ depend on both:
   number of chunk leaves does not give the code's length; `code_size`
   in the basic data leaf does.
 
-The thirteen cases and what each one covers:
+The fifteen cases and what each one covers:
 
 | Name | Covers |
 | --- | --- |
@@ -198,5 +198,7 @@ The thirteen cases and what each one covers:
 | `shared_bytecode_two_accounts` | Two accounts with identical 129-chunk code. Their header chunks are per-account and disjoint; the one overflowing chunk is content-addressed and must land on a single shared leaf, so the state has 261 leaves rather than 262. |
 | `delegation_designator` | An EIP-7702 designator, `0xef0100` followed by an address: 23 bytes, one header chunk, the only protocol-reachable code change on an existing account. |
 | `code_chunks_of_zero_bytes` | 62 zero bytes of code: both chunks are 32 zero bytes and are absent, so the account commits no chunk leaf at all while its `code_size` stays 62. |
+| `zero_code_chunk_in_the_code_zone` | 160 chunks of code with an all-zero chunk at 130, in the content-addressed code zone, and another at 5 in the account header. `code_chunks_of_zero_bytes` reaches header chunks only; the two zones are written on separate paths, so applying the zero rule to one of them still yields a root. |
+| `shared_bytecode_with_a_zero_overflow_chunk` | Two accounts running the code above. The zero code-zone chunk has to be absent from the single leaf they would otherwise share, so absence and content addressing have to compose. |
 | `max_basic_data_fields` | A balance of `2**128 - 1`, the largest the 16-byte field holds, beside the largest JSON-safe nonce. A balance of `2**128` or more cannot be committed at all. |
 | `random_6_accounts_seed_8297` | Six pseudo-random accounts with mixed code lengths, scattered storage, and full-width balances, as a broad spread over the composition. |