fix(antigravity): parse retry-after delay from 429 response body

When receiving HTTP 429 (Too Many Requests) responses, parse the retry
delay from the response body using parseRetryDelay and populate the
statusErr.retryAfter field. This allows upstream callers to respect
the server's requested retry timing.

Applied to all error paths in Execute, executeClaudeNonStream,
ExecuteStream, CountTokens, and refreshToken functions.

internal/runtime/executor/antigravity_executor.go

@@ -155,7 +155,13 @@ func (e *AntigravityExecutor) Execute(ctx context.Context, auth *cliproxyauth.Au
 				log.Debugf("antigravity executor: rate limited on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
 				continue
 			}
-			err = statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+			sErr := statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+			if httpResp.StatusCode == http.StatusTooManyRequests {
+				if retryAfter, parseErr := parseRetryDelay(bodyBytes); parseErr == nil && retryAfter != nil {
+					sErr.retryAfter = retryAfter
+				}
+			}
+			err = sErr
 			return resp, err
 		}
 
@@ -169,7 +175,13 @@ func (e *AntigravityExecutor) Execute(ctx context.Context, auth *cliproxyauth.Au
 
 	switch {
 	case lastStatus != 0:
-		err = statusErr{code: lastStatus, msg: string(lastBody)}
+		sErr := statusErr{code: lastStatus, msg: string(lastBody)}
+		if lastStatus == http.StatusTooManyRequests {
+			if retryAfter, parseErr := parseRetryDelay(lastBody); parseErr == nil && retryAfter != nil {
+				sErr.retryAfter = retryAfter
+			}
+		}
+		err = sErr
 	case lastErr != nil:
 		err = lastErr
 	default:
@@ -259,7 +271,13 @@ func (e *AntigravityExecutor) executeClaudeNonStream(ctx context.Context, auth *
 				log.Debugf("antigravity executor: rate limited on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
 				continue
 			}
-			err = statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+			sErr := statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+			if httpResp.StatusCode == http.StatusTooManyRequests {
+				if retryAfter, parseErr := parseRetryDelay(bodyBytes); parseErr == nil && retryAfter != nil {
+					sErr.retryAfter = retryAfter
+				}
+			}
+			err = sErr
 			return resp, err
 		}
 
@@ -324,7 +342,13 @@ func (e *AntigravityExecutor) executeClaudeNonStream(ctx context.Context, auth *
 
 	switch {
 	case lastStatus != 0:
-		err = statusErr{code: lastStatus, msg: string(lastBody)}
+		sErr := statusErr{code: lastStatus, msg: string(lastBody)}
+		if lastStatus == http.StatusTooManyRequests {
+			if retryAfter, parseErr := parseRetryDelay(lastBody); parseErr == nil && retryAfter != nil {
+				sErr.retryAfter = retryAfter
+			}
+		}
+		err = sErr
 	case lastErr != nil:
 		err = lastErr
 	default:
@@ -599,7 +623,13 @@ func (e *AntigravityExecutor) ExecuteStream(ctx context.Context, auth *cliproxya
 				log.Debugf("antigravity executor: rate limited on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
 				continue
 			}
-			err = statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+			sErr := statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+			if httpResp.StatusCode == http.StatusTooManyRequests {
+				if retryAfter, parseErr := parseRetryDelay(bodyBytes); parseErr == nil && retryAfter != nil {
+					sErr.retryAfter = retryAfter
+				}
+			}
+			err = sErr
 			return nil, err
 		}
 
@@ -654,7 +684,13 @@ func (e *AntigravityExecutor) ExecuteStream(ctx context.Context, auth *cliproxya
 
 	switch {
 	case lastStatus != 0:
-		err = statusErr{code: lastStatus, msg: string(lastBody)}
+		sErr := statusErr{code: lastStatus, msg: string(lastBody)}
+		if lastStatus == http.StatusTooManyRequests {
+			if retryAfter, parseErr := parseRetryDelay(lastBody); parseErr == nil && retryAfter != nil {
+				sErr.retryAfter = retryAfter
+			}
+		}
+		err = sErr
 	case lastErr != nil:
 		err = lastErr
 	default:
@@ -795,12 +831,24 @@ func (e *AntigravityExecutor) CountTokens(ctx context.Context, auth *cliproxyaut
 			log.Debugf("antigravity executor: rate limited on base url %s, retrying with fallback base url: %s", baseURL, baseURLs[idx+1])
 			continue
 		}
-		return cliproxyexecutor.Response{}, statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+		sErr := statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+		if httpResp.StatusCode == http.StatusTooManyRequests {
+			if retryAfter, parseErr := parseRetryDelay(bodyBytes); parseErr == nil && retryAfter != nil {
+				sErr.retryAfter = retryAfter
+			}
+		}
+		return cliproxyexecutor.Response{}, sErr
 	}
 
 	switch {
 	case lastStatus != 0:
-		return cliproxyexecutor.Response{}, statusErr{code: lastStatus, msg: string(lastBody)}
+		sErr := statusErr{code: lastStatus, msg: string(lastBody)}
+		if lastStatus == http.StatusTooManyRequests {
+			if retryAfter, parseErr := parseRetryDelay(lastBody); parseErr == nil && retryAfter != nil {
+				sErr.retryAfter = retryAfter
+			}
+		}
+		return cliproxyexecutor.Response{}, sErr
 	case lastErr != nil:
 		return cliproxyexecutor.Response{}, lastErr
 	default:
@@ -963,7 +1011,13 @@ func (e *AntigravityExecutor) refreshToken(ctx context.Context, auth *cliproxyau
 	}
 
 	if httpResp.StatusCode < http.StatusOK || httpResp.StatusCode >= http.StatusMultipleChoices {
-		return auth, statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+		sErr := statusErr{code: httpResp.StatusCode, msg: string(bodyBytes)}
+		if httpResp.StatusCode == http.StatusTooManyRequests {
+			if retryAfter, parseErr := parseRetryDelay(bodyBytes); parseErr == nil && retryAfter != nil {
+				sErr.retryAfter = retryAfter
+			}
+		}
+		return auth, sErr
 	}
 
 	var tokenResp struct {