Fix panic on GET /chunked from integer overflow

HttpServerTimeout is a time.Duration (nanoseconds); the default-delay
branch scaled it by time.Second again, overflowing int64 to a negative
value and passing it to rand.Intn, which panics. The bare /chunked route
(no wait param) hit this on every request.

Convert the timeout to whole seconds in a guarded helper that keeps
rand.Intn's argument positive, and add a regression test.

pkg/api/http/chunked.go

@@ -26,7 +26,7 @@ func (s *Server) chunkedHandler(w http.ResponseWriter, r *http.Request) {
 
 	delay, err := strconv.Atoi(vars["wait"])
 	if err != nil {
-		delay = rand.Intn(int(s.config.HttpServerTimeout*time.Second)-10) + 10
+		delay = randomDelaySeconds(s.config.HttpServerTimeout)
 	}
 
 	flusher, ok := w.(http.Flusher)
@@ -46,3 +46,15 @@ func (s *Server) chunkedHandler(w http.ResponseWriter, r *http.Request) {
 
 	flusher.Flush()
 }
+
+// randomDelaySeconds returns a random delay in seconds within [10, timeout),
+// used when no explicit wait is provided. timeout is a time.Duration, so it is
+// converted to whole seconds; the upper bound is clamped to keep rand.Intn's
+// argument positive (it panics on a non-positive argument).
+func randomDelaySeconds(timeout time.Duration) int {
+	maxDelay := int(timeout / time.Second)
+	if maxDelay <= 11 {
+		maxDelay = 12
+	}
+	return rand.Intn(maxDelay-10) + 10
+}

pkg/api/http/chunked_test.go

@@ -5,6 +5,7 @@ import (
 	"net/http/httptest"
 	"regexp"
 	"testing"
+	"time"
 )
 
 func TestChunkedHandler(t *testing.T) {
@@ -33,3 +34,19 @@ func TestChunkedHandler(t *testing.T) {
 			rr.Body.String(), expected)
 	}
 }
+
+// TestRandomDelaySeconds covers the default-delay branch taken by the bare
+// /chunked route (no {wait} value). This used to panic because the
+// duration-to-seconds math overflowed int64 and handed rand.Intn a negative
+// argument. Every timeout must yield a valid delay in [10, max] without panicking.
+func TestRandomDelaySeconds(t *testing.T) {
+	timeouts := []time.Duration{30 * time.Second, 12 * time.Second, time.Second, 0, -1}
+	for _, timeout := range timeouts {
+		for range 100 {
+			d := randomDelaySeconds(timeout)
+			if d < 10 {
+				t.Fatalf("timeout %s: delay %d below floor of 10", timeout, d)
+			}
+		}
+	}
+}