Function diff_entries 

pub fn diff_entries(
    prev: &[TrackedEntry],
    current: Vec<PortEntry>,
    now: Instant,
) -> Vec<TrackedEntry>

Compute entry diffs between the previous and current scan.

Returns a merged list where:

• Entries present in current but not prev are EntryStatus::New
• Entries present in both are EntryStatus::Unchanged
• Entries in prev but not current are EntryStatus::Gone

Already-gone entries from prev are dropped (no double-gone). Identity key: (local_port, pid).