Validate a decoded sidecar against the actual source identity. The index-first open path calls this before trusting the sidecar; on false it must fall back to a cold scan.
The decoded sidecar.
The actual source length.
The actual source hash.
True if the sidecar matches the source.
Validate a decoded sidecar against the actual source identity. The index-first open path calls this before trusting the sidecar; on false it must fall back to a cold scan.