feature: sent-PDF history (10) + image retention (30) with pruning per Ben's 2026-09-02 ruling

Sources/Shotdeck/SendController.swift

@@ -100,6 +100,8 @@ extension AppModel: SendCapable {
     /// `NSSharingServiceDelegate.sharingService(_:didShareItems:)` seam.
     func handleDidShareItems(fileName: String, pageCount: Int) async {
         guard !session.isEmpty else { return }
+        let sentSessionID = session.id
+        let sourceURL = lastComposedPDFURL ?? outboxURL.appendingPathComponent(fileName)
         do {
             _ = try await spool.archiveCurrent(pdfFileName: fileName)
             replaceSession(try await spool.currentSession())
@@ -107,6 +109,20 @@ extension AppModel: SendCapable {
             setStatus("Sent — \(pageCount) \(pageWord).")
         } catch {
             setStatus((error as? ShotdeckError)?.errorDescription ?? "Could not archive the session.")
+            return
+        }
+        do {
+            _ = try await historyStore.recordSentPDF(
+                sourceURL: sourceURL,
+                sessionID: sentSessionID,
+                pageCount: pageCount,
+                sentAt: Date()
+            )
+            try await historyStore.pruneImages()
+        } catch {
+            Log.spool.error(
+                "Could not record sent PDF into history at \(sourceURL.path, privacy: .public): \(error.localizedDescription, privacy: .public)"
+            )
         }
     }