fix(core): транзиентный 401 теперь ретраится для GET

isRetryable (core/http.go): добавлен StatusUnauthorized (401) к {429,502,503,504}.
Gateway может временно отклонять валидный JWT — без этого одиночный 401 ронял
read/plan/поллинг.

- client_test.go: юнит-тест TestIsRetryable (401/429/502/503/504 = true; 400/403/404/500 = false).
- ARCHITECTURE.md: раздел API Resilience приведён к фактическому поведению
  (401 реализован; POST не ретраится намеренно).

Проверено: go build ./... OK; go test ./internal/core/... -short OK.

TOOLS/ARCHITECTURE.md

@@ -123,9 +123,11 @@ Each operation has a kind:
 
 - Core MUST retry transient 401 errors from Gateway (3 attempts, exponential backoff).
   Gateway may temporarily reject valid JWT tokens.
-- **CURRENTLY NOT IMPLEMENTED** — `isRetryable` (`core/http.go`) retries only
-  {429, 502, 503, 504}, NOT 401, and only for GET. This is a known gap versus the
-  intent above; fix in `core/http.go` `isRetryable`.
+- Implemented: `isRetryable` (`core/http.go`) includes 401 alongside {429, 502, 503, 504};
+  retry applies to GET requests only.
+- Network errors and HTTP retryable statuses are retried for **GET only**. POST is not
+  retried (a blind retry of the creating `POST /instanceOperations` could duplicate an
+  operation — see open question on idempotency).
 
 ### Generated Code Resilience
 

provider/internal/core/client_test.go

@@ -52,6 +52,33 @@ func TestNormalizeValue_TrimSpace(t *testing.T) {
 	}
 }
 
+func TestIsRetryable(t *testing.T) {
+	retryable := []int{
+		http.StatusUnauthorized,      // 401 — транзиентный отказ Gateway
+		http.StatusTooManyRequests,   // 429
+		http.StatusServiceUnavailable, // 503
+		http.StatusBadGateway,        // 502
+		http.StatusGatewayTimeout,    // 504
+	}
+	for _, code := range retryable {
+		if !isRetryable(code) {
+			t.Errorf("expected isRetryable(%d)=true", code)
+		}
+	}
+
+	notRetryable := []int{
+		http.StatusBadRequest,          // 400
+		http.StatusForbidden,           // 403
+		http.StatusNotFound,            // 404
+		http.StatusInternalServerError, // 500
+	}
+	for _, code := range notRetryable {
+		if isRetryable(code) {
+			t.Errorf("expected isRetryable(%d)=false", code)
+		}
+	}
+}
+
 // ===== waitForOperationFinish tests =====
 
 func makeTestClient(handler http.HandlerFunc) (*UniversalClient, func()) {

provider/internal/core/http.go

@@ -117,8 +117,11 @@ func (c *UniversalClient) doRequest(ctx context.Context, method, path string, pa
 }
 
 // isRetryable returns true for transient HTTP errors that can be retried.
+// 401 включён: Gateway может транзиентно отклонять валидный JWT (см. ARCHITECTURE.md,
+// «API Resilience»). Ретраится только для GET (см. условие в doRequest).
 func isRetryable(statusCode int) bool {
-	return statusCode == http.StatusTooManyRequests || // 429
+	return statusCode == http.StatusUnauthorized || // 401
+		statusCode == http.StatusTooManyRequests || // 429
 		statusCode == http.StatusServiceUnavailable || // 503
 		statusCode == http.StatusBadGateway || // 502
 		statusCode == http.StatusGatewayTimeout // 504