fix(core): carry duplicates through the import audit event

success no longer includes dedup-skipped mail, so without a
duplicates field ImportPerformed consumers could not tell an
all-duplicates batch from one that silently lost everything. Also
documents that ExtractOutcome::Imported covers mail dropped by
archive rules, which has always counted as a success.

crates/core/src/envelope/extractor.rs

@@ -46,8 +46,10 @@ use crate::{
     utils::{compute_content_hash, hex_hash, html::extract_text},
 };
 
-/// The outcome of extracting an envelope: either the message was imported,
-/// or it was skipped because its content hash was already archived.
+/// The outcome of extracting an envelope. `Duplicate` means the message was
+/// skipped because its content hash was already archived. `Imported` covers
+/// every other processed message, including mail dropped by archive rules,
+/// which has always counted as a success on the import surfaces.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 #[must_use]
 pub enum ExtractOutcome {

crates/core/src/ext/event_bus.rs

@@ -209,6 +209,7 @@ pub enum Event {
         format: String,
         total: u64,
         success: u64,
+        duplicates: u64,
         failed: u64,
     },
     MailboxRemoved {

crates/server/src/rest/api/import.rs

@@ -77,6 +77,7 @@ impl ImportApi {
             format: "eml".to_string(),
             total: result.total as u64,
             success: result.success as u64,
+            duplicates: result.duplicates as u64,
             failed: result.failed as u64,
         });
 
@@ -274,6 +275,7 @@ impl ImportApi {
             format: format_str.clone(),
             total: 0,
             success: 0,
+            duplicates: 0,
             failed: 0,
         });
         tokio::task::spawn_blocking(move || {