feat(webicached): rescan conf dir each batch, prioritize new packages

Rescans the conf directory at the start of each batch loop so new
{pkg}/releases.conf files dropped on disk are picked up without a restart.

Also runs a rescan after each individual package refresh mid-batch. If a
new conf is discovered, the inner loop breaks immediately so the outer
loop recomputes staleness — new packages have a zero timestamp and sort
to position 1, meaning they are fetched in the very next slot.

cmd/webicached/main.go

@@ -206,11 +206,11 @@ func main() {
 	if err != nil {
 		log.Fatalf("discover: %v", err)
 	}
+	nameSet := make(map[string]bool, len(filterPkgs))
+	for _, a := range filterPkgs {
+		nameSet[a] = true
+	}
 	if len(filterPkgs) > 0 {
-		nameSet := make(map[string]bool, len(filterPkgs))
-		for _, a := range filterPkgs {
-			nameSet[a] = true
-		}
 		var filtered []pkgConf
 		for _, p := range packages {
 			if nameSet[p.name] {
@@ -227,8 +227,41 @@ func main() {
 		}
 	}
 
+	// rescanNew appends any conf files added since the last scan.
+	// Returns true when at least one new package was added so the caller
+	// can restart the batch loop and process new packages immediately.
+	rescanNew := func() bool {
+		discovered, err := discover(wc.ConfDir)
+		if err != nil {
+			log.Printf("rescan: %v", err)
+			return false
+		}
+		known := make(map[string]bool, len(real))
+		for _, p := range real {
+			known[p.name] = true
+		}
+		added := false
+		for _, p := range discovered {
+			if p.conf.AliasOf != "" || known[p.name] {
+				continue
+			}
+			if len(filterPkgs) > 0 && !nameSet[p.name] {
+				continue
+			}
+			log.Printf("discovered new package: %s (source=%s)", p.name, p.conf.Source)
+			real = append(real, p)
+			added = true
+		}
+		return added
+	}
+
 	log.Printf("refreshing %d packages, interval %s, batch size 20 (ctrl-c to stop)", len(real), cfg.interval)
 	for {
+		// Rescan before computing staleness so newly added conf files are
+		// included immediately. New packages have a zero timestamp and sort
+		// to the front of the stale list, so they are processed next.
+		rescanNew()
+
 		stale := wc.stalest(real)
 		if len(stale) == 0 {
 			log.Printf("all packages fresh, sleeping %s", cfg.interval)
@@ -252,6 +285,10 @@ func main() {
 			}
 			cancel()
 			time.Sleep(cfg.interval)
+			// Rescan mid-batch so new packages preempt remaining batch items.
+			if rescanNew() {
+				break
+			}
 		}
 	}
 }