fix(cluster)!: rename X-Upkeep-Secret header to X-Uptop-Secret

Last upkeep-era name in the wire protocol. Breaking for mixed-version
clusters, but zero installed base exists pre-v0.1.0 — free now, breaking
forever after first tag.

internal/cluster/cluster.go

@@ -52,7 +52,7 @@ func runFollowerLoop(ctx context.Context, cfg Config, eng *monitor.Engine) {
 
 		req, _ := http.NewRequest("GET", cfg.PeerURL+"/api/health", nil)
 		if cfg.SharedKey != "" {
-			req.Header.Set("X-Upkeep-Secret", cfg.SharedKey)
+			req.Header.Set("X-Uptop-Secret", cfg.SharedKey)
 		}
 
 		resp, err := client.Do(req)

internal/cluster/cluster_test.go

@@ -113,7 +113,7 @@ func TestFollowerLoop_SendsSecret(t *testing.T) {
 	var receivedSecret string
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		mu.Lock()
-		receivedSecret = r.Header.Get("X-Upkeep-Secret")
+		receivedSecret = r.Header.Get("X-Uptop-Secret")
 		mu.Unlock()
 		w.WriteHeader(200)
 		w.Write([]byte("OK"))

internal/cluster/probe.go

@@ -90,7 +90,7 @@ func probeRegister(ctx context.Context, client *http.Client, cfg ProbeConfig) er
 		return err
 	}
 	req.Header.Set("Content-Type", "application/json")
-	req.Header.Set("X-Upkeep-Secret", cfg.SharedKey)
+	req.Header.Set("X-Uptop-Secret", cfg.SharedKey)
 	resp, err := client.Do(req)
 	if err != nil {
 		return err
@@ -108,7 +108,7 @@ func probeFetchAssignments(ctx context.Context, client *http.Client, cfg ProbeCo
 	if err != nil {
 		return nil, err
 	}
-	req.Header.Set("X-Upkeep-Secret", cfg.SharedKey)
+	req.Header.Set("X-Uptop-Secret", cfg.SharedKey)
 	resp, err := client.Do(req)
 	if err != nil {
 		return nil, err
@@ -180,7 +180,7 @@ func probeReportResults(ctx context.Context, client *http.Client, cfg ProbeConfi
 		return err
 	}
 	req.Header.Set("Content-Type", "application/json")
-	req.Header.Set("X-Upkeep-Secret", cfg.SharedKey)
+	req.Header.Set("X-Uptop-Secret", cfg.SharedKey)
 	resp, err := client.Do(req)
 	if err != nil {
 		return err

internal/server/server.go

@@ -127,7 +127,7 @@ func (s *Server) routes() http.Handler {
 }
 
 func (s *Server) requireAuth(r *http.Request) bool {
-	return s.cfg.ClusterKey != "" && checkSecret(r.Header.Get("X-Upkeep-Secret"), s.cfg.ClusterKey)
+	return s.cfg.ClusterKey != "" && checkSecret(r.Header.Get("X-Uptop-Secret"), s.cfg.ClusterKey)
 }
 
 func (s *Server) handlePush(w http.ResponseWriter, r *http.Request) {
@@ -159,7 +159,7 @@ func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
 		return
 	}
-	if s.cfg.ClusterKey != "" && !checkSecret(r.Header.Get("X-Upkeep-Secret"), s.cfg.ClusterKey) {
+	if s.cfg.ClusterKey != "" && !checkSecret(r.Header.Get("X-Uptop-Secret"), s.cfg.ClusterKey) {
 		http.Error(w, "Unauthorized", http.StatusUnauthorized)
 		return
 	}

internal/server/server_test.go

@@ -141,7 +141,7 @@ func authReq(method, url, secret string, body []byte) (*http.Response, error) {
 		return nil, err
 	}
 	if secret != "" {
-		req.Header.Set("X-Upkeep-Secret", secret)
+		req.Header.Set("X-Uptop-Secret", secret)
 	}
 	return http.DefaultClient.Do(req)
 }