fix: detect context length errors in GCP Vertex AI provider (aaif-goose#6976)

Signed-off-by: rabi <ramishra@redhat.com>

Author: rabi

crates/goose/src/providers/gcpvertexai.rs

@@ -26,6 +26,7 @@ use crate::providers::formats::gcpvertexai::{
     ModelProvider, RequestContext, DEFAULT_MODEL, KNOWN_MODELS,
 };
 use crate::providers::gcpauth::GcpAuth;
+use crate::providers::openai_compatible::map_http_error_to_provider_error;
 use crate::providers::retry::RetryConfig;
 use crate::providers::utils::RequestLog;
 use crate::session_context::SESSION_ID_HEADER;
@@ -351,9 +352,8 @@ impl GcpVertexAIProvider {
                 )));
             } else {
                 let response_text = response.text().await.unwrap_or_default();
-                return Err(ProviderError::RequestFailed(format!(
-                    "Request failed with status {status}: {response_text}"
-                )));
+                let payload = serde_json::from_str::<Value>(&response_text).ok();
+                return Err(map_http_error_to_provider_error(status, payload));
             }
         }
     }