Function buffer_fully_embedded 

pub fn buffer_fully_embedded(
    storage: &SqliteStorage,
    buffer_id: i64,
) -> Result<bool>

Checks if a buffer has all chunks embedded.

Uses a single SQL query (NOT EXISTS) instead of per-chunk lookups, reducing database round-trips from O(n) to O(1) for a buffer with n chunks.

Errors

Returns an error if the check fails.