execution/types/accounts, db/state/execctx: extract codeHash without a full account decode

[yperbasis]

Split from #22159 (the #22120 StateCache review findings — finding 7's decode-cost half).

What changed

codeHashForAddr fully decoded every account record it touched — balance parse plus codeHash interning per mem hit — just to read one field. accounts.DeserialiseV3CodeHash parses the SerialiseV3 layout only up to and including the codeHash field:

• bounds-safe on every truncation point (returns nil on malformed input; the full decoder indexes without length checks),
• returns nil for both no-code sentinel spellings (zero hash, empty-code keccak), matching CodeHash.IsEmpty,
• returns a subslice of enc, valid only while enc is — all four call sites in codeHashForAddr consume it synchronously within the tx, and the one retained copy (PutAddrCodeHash) goes through a fixed [32]byte.

decodeAccountCodeHash is deleted; its call sites switch to the extractor.

Testing

• TestDeserialiseV3CodeHash cross-validates the extractor against the full DeserialiseV3 decode over a nonce × balance × codeHash × incarnation matrix.
• TestDeserialiseV3CodeHashMalformed walks every truncation point of a record (nil at any cut into the codeHash, the hash beyond it), rejects non-32-byte codeHash fields, and pins the sentinel spellings to nil.

Verification: execution/types/accounts + db/state/execctx suites, repeated clean make lint.

Touches domain_shared.go in hunks disjoint from #22467; the two merge independently.

[Copilot]

Pull request overview

This PR optimizes the fast-path code-hash lookup by extracting the codeHash field directly from SerialiseV3-encoded account bytes, avoiding the cost of a full account decode (notably balance parsing and CodeHash interning) when only the hash is needed.

Changes:

• Added accounts.DeserialiseV3CodeHash(enc []byte) []byte to extract the 32-byte code hash (or return nil for malformed/no-code cases) without full decoding.
• Updated SharedDomains.codeHashForAddr to use the new extractor and removed the now-redundant decodeAccountCodeHash.
• Added test coverage validating equivalence vs full DeserialiseV3 and ensuring bounds-safety across truncation/malformed cases.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
execution/types/accounts/account.go	Adds a bounds-safe extractor for the codeHash field from SerialiseV3 account encoding.
execution/types/accounts/account_test.go	Adds tests for correctness vs full decode and malformed/truncation behavior.
db/state/execctx/domain_shared.go	Switches codeHashForAddr to the new extractor and removes the full-decode helper.

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[AskAlexSharov]

can: if ch := common.Hash(h); ch == (common.Hash{}) || ch == empty.CodeHash {

[yperbasis]

Done in 6c04496 — switched to the direct common.Hash comparison and removed the bytes import. Thanks.