docs: document P256 ERC-7913 key format

[phrwlk]

Add NatSpec in ERC7913P256Verifier.sol to explicitly state the required key format for P256 ERC‑7913 verifiers: 64‑byte concatenation qx || qy, each 32‑byte big‑endian. Clarifies that SEC1 prefixes are not accepted and compressed keys are not supported.
Purpose: eliminate ambiguity for integrators; align with code behavior (key.length == 0x40 and bytes32 slicing) and sibling ERC7913WebAuthnVerifier documentation; prevent misuse with SEC1/uncompressed/compressed encodings.

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Latest commit: 978332c

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[coderabbitai]

Walkthrough

Documentation was added to the header comment of the ERC7913P256Verifier.sol file to specify the key format requirements. The documentation clarifies that keys must be 64-byte concatenations of P256 coordinates qx and qy, with each coordinate formatted as 32-byte big-endian values. The documentation also notes that SEC1 prefixes and compressed keys are not supported. No code or logic modifications were made to the verification functionality.

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'docs: document P256 ERC-7913 key format' clearly and concisely summarizes the main change: adding documentation about the P256 key format requirement for ERC-7913 verifiers.
Description check	✅ Passed	The description is directly related to the changeset, explaining the purpose of adding NatSpec documentation about the P256 key format requirements, existing code behavior alignment, and preventing misuse.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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• contracts/utils/cryptography/verifiers/ERC7913P256Verifier.sol (1 hunks)

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🔇 Additional comments (1)

contracts/utils/cryptography/verifiers/ERC7913P256Verifier.sol (1)

12-15: Documentation accurately reflects code behavior and requirements.

The NatSpec documentation correctly specifies the P-256 key format requirements:

• The 64-byte length requirement aligns with the key.length == 0x40 check on line 23
• The coordinate extraction as 32-byte big-endian values matches the bytes32 slicing on lines 24-25
• The restrictions on SEC1 prefixes and compressed keys are inherent to the strict 64-byte length requirement

The documentation is clear, concise, and sufficiently explicit about what formats are not accepted. This will help prevent misuse and misunderstandings.

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