v0.21.1: Add GET /api/config endpoint for live config content

New endpoint returns raw controller.yaml content (text/yaml) for Hub
live diff and pull operations. Same auth as other config endpoints.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/api/router.go

@@ -89,6 +89,10 @@ func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	case path == "/config/hash" && req.Method == http.MethodGet:
 		r.configHash(w, req)
 
+	// GET /api/config — return raw controller.yaml content
+	case path == "/config" && req.Method == http.MethodGet:
+		r.configContent(w, req)
+
 	// GET /api/stacks/{name}/deploy-fields
 	case hasSuffix(path, "/deploy-fields") && req.Method == http.MethodGet:
 		r.getDeployFields(w, req, extractName(path, "/deploy-fields"))
@@ -978,6 +982,16 @@ func (r *Router) configHash(w http.ResponseWriter, _ *http.Request) {
 	writeJSON(w, http.StatusOK, apiResponse{OK: true, Data: map[string]string{"hash": hash, "path": filepath.Base(r.configPath)}})
 }
 
+func (r *Router) configContent(w http.ResponseWriter, _ *http.Request) {
+	data, err := os.ReadFile(r.configPath)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, apiResponse{OK: false, Error: "failed to read config"})
+		return
+	}
+	w.Header().Set("Content-Type", "text/yaml; charset=utf-8")
+	w.Write(data)
+}
+
 func writeJSON(w http.ResponseWriter, status int, v interface{}) {
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(status)