Function validate_snapshot_compatibility 

pub fn validate_snapshot_compatibility(
    snapshot: &NormalizedFingerprintSnapshot,
) -> Result<(), SnapshotCompatibilityError>

Validate normalized snapshot compatibility rules across modes and versions.

Current compatibility contract:

• supports schema major version 1
• requires signals.tls for SnapshotMode::Http
• requires signals.webgl for SnapshotMode::Browser
• requires deprecated mirror fields, when present, to match canonical fields

Errors

Returns SnapshotCompatibilityError when schema version is invalid or unsupported, required mode-specific signals are missing, or legacy mirror fields do not match canonical signal values.