fix(verifier): return structured verification reports instead of lossy booleans in WASM bindings

[bordumb]

Description

In crates/auths-verifier/src/wasm.rs (lines 154-191), WASM verification helpers such as wasm_verify_artifact_signature return a plain bool (false) for all failure cases:

#[wasm_bindgen(js_name = verifyArtifactSignature)]
pub async fn wasm_verify_artifact_signature(
    file_hash_hex: &str,
    signature_hex: &str,
    public_key_hex: &str,
    curve: Option<String>,
) -> bool {
    if file_hash_hex.len() > MAX_FILE_HASH_HEX_LEN ... {
        return false;
    }
    let Ok(hash_bytes) = hex::decode(file_hash_hex) else { return false; };
    let Ok(sig_bytes) = hex::decode(signature_hex) else { return false; };
    let Ok(pk_bytes) = hex::decode(public_key_hex) else { return false; };
    ...
}

Root Cause

When verification returns false, calling JS code cannot determine whether the failure was caused by invalid hex encoding, incorrect signature byte lengths (sig_bytes.len() != 64), input size exceeding bounds, or an actual cryptographic signature check failure.

Expected Behavior

WASM export functions should return a structured Result JSON object or WasmVerificationResult containing explicit error messages and error codes (e.g. InvalidHex, InvalidSignatureLength, SignatureMismatch) instead of losing error context via raw bool returns.

Location

• crates/auths-verifier/src/wasm.rs