fix(gemini): handle 'Stream ended' gracefully and improve debug logging

src/providers/gemini.rs

@@ -848,11 +848,12 @@ impl super::Provider for GeminiProvider {
                         let gemini_response: GeminiStreamResponse = serde_json::from_str(&msg.data)
                             .map_err(|e| AppError::ProviderError(format!("Failed to parse stream chunk: {}", e)))?;
                         
-                        tracing::info!("Received Gemini stream chunk (candidates: {}, has_usage: {})", 
+                        tracing::info!("Received Gemini stream chunk (candidates: {}, has_usage: {}, finish_reason: {:?})", 
                             gemini_response.candidates.len(), 
-                            gemini_response.usage_metadata.is_some()
+                            gemini_response.usage_metadata.is_some(),
+                            gemini_response.candidates.first().and_then(|c| c.finish_reason.as_deref())
                         );
-                        
+
                         // Extract usage from usageMetadata if present (reported on every/last chunk)
                         let stream_usage = gemini_response.usage_metadata.as_ref().map(|u| {
                             super::StreamUsage {
@@ -967,6 +968,12 @@ impl super::Provider for GeminiProvider {
                     }
                     Ok(_) => continue,
                     Err(e) => {
+                        // "Stream ended" is usually a normal EOF signal in reqwest-eventsource.
+                        // We check the string representation to avoid returning it as an error.
+                        if e.to_string().contains("Stream ended") {
+                            break;
+                        }
+
                         // On stream error, attempt to probe for the actual error body from the provider
                         let probe_resp = probe_client
                             .post(&probe_url)