fix: address PR review — timer drain, header clone, doc comment

- Drain timer.C after Stop to prevent spurious immediate wake on
  first loop iteration (0-duration timer fires before Reset)
- Clone header value slices in rewriteRequest to decouple from
  caller's request and prevent data races on retry
- Update WithReadyQueueSize doc comment: default is 500, not 4000

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: myleshorton

domainfront.go

@@ -80,7 +80,7 @@ func WithClientHelloID(id tls.ClientHelloID) Option {
 func WithCrawlerConcurrency(n int) Option { return func(c *Client) { c.crawlerConcurrency = n } }
 
 // WithReadyQueueSize sets the capacity of the ready-fronts channel.
-// Smaller values save memory on constrained devices. Default is 4000.
+// Smaller values save memory on constrained devices. Default is 500.
 func WithReadyQueueSize(n int) Option { return func(c *Client) { c.readyQueueSize = n } }
 
 // WithCacheSaveInterval sets how often dirty cache state is flushed to disk.
@@ -246,7 +246,11 @@ func (c *Client) crawler() {
 	// Use a reusable timer instead of time.After to avoid leaking timers.
 	// time.After creates a new timer each iteration that isn't GC'd until it
 	// fires — on memory-constrained devices this creates mounting GC pressure.
+	// Initialize stopped and drain to avoid an immediate spurious wake.
 	timer := time.NewTimer(0)
+	if !timer.Stop() {
+		<-timer.C
+	}
 	defer timer.Stop()
 
 	for {

roundtrip.go

@@ -143,11 +143,13 @@ func rewriteRequest(req *http.Request, frontedHost string, body io.ReadCloser) *
 		Header:        make(http.Header, len(req.Header)),
 	}).WithContext(req.Context())
 
-	// Share header value slices instead of copying them. This is safe because
-	// the original request's headers aren't modified during the round trip.
+	// Clone header value slices to decouple from the caller's request.
+	// Sharing slices can cause data races if the original request is reused.
 	for k, vs := range req.Header {
 		if !strings.EqualFold(k, "Host") {
-			r.Header[k] = vs
+			cp := make([]string, len(vs))
+			copy(cp, vs)
+			r.Header[k] = cp
 		}
 	}
 	return r