fix(agent/sync): handle multiple /v1/models response formats

The upstream AI endpoint returns an OpenAI-compatible format, but the
response body parsing was fragile. Make it resilient:
1. Try standard OpenAI format: { "data": [{id}, ...] }
2. Try raw array: [{id}, ...]
3. Try alternate format: { "models": [{id}, ...] }
4. Log actual response body (first 500 chars) when all formats fail

Also adds a warning log with the raw response on parse failure so
future debugging is straightforward.

libs/service/agent/sync.rs

@@ -680,6 +680,10 @@ struct ModelEntry {
 }
 
 /// List accessible model IDs from the AI endpoint.
+/// Supports multiple response formats:
+///   - OpenAI: `{ "data": [{"id": "..."}, ...] }`
+///   - Array: `[{"id": "..."}, ...]`
+///   - Custom: `{ "models": [{"id": "..."}, ...] }`
 async fn list_accessible_models(
     client: &reqwest::Client,
     base_url: &str,
@@ -693,12 +697,35 @@ async fn list_accessible_models(
         .await
         .map_err(|e| AppError::InternalServerError(format!("failed to list models: {}", e)))?;
 
-    let body: ModelsListResponse = resp
-        .json()
+    let body = resp
+        .text()
         .await
-        .map_err(|e| AppError::InternalServerError(format!("failed to parse models response: {}", e)))?;
+        .map_err(|e| AppError::InternalServerError(format!("failed to read models body: {}", e)))?;
 
-    Ok(body.data.into_iter().map(|m| m.id).collect())
+    // Try OpenAI format: { "data": [{"id": "..."}, ...] }
+    if let Ok(parsed) = serde_json::from_str::<ModelsListResponse>(&body) {
+        return Ok(parsed.data.into_iter().map(|m| m.id).collect());
+    }
+
+    // Try raw array: [{"id": "..."}, ...]
+    if let Ok(parsed) = serde_json::from_str::<Vec<ModelEntry>>(&body) {
+        return Ok(parsed.into_iter().map(|m| m.id).collect());
+    }
+
+    // Try { "models": [{"id": "..."}, ...] }
+    #[derive(Debug, Deserialize)]
+    struct ModelsAltResponse {
+        models: Vec<ModelEntry>,
+    }
+    if let Ok(parsed) = serde_json::from_str::<ModelsAltResponse>(&body) {
+        return Ok(parsed.models.into_iter().map(|m| m.id).collect());
+    }
+
+    tracing::warn!(body = %body.chars().take(500).collect::<String>(), "list_accessible_models: unknown response format");
+    Err(AppError::InternalServerError(format!(
+        "unexpected /v1/models response format (first 200 chars): {}",
+        body.chars().take(200).collect::<String>()
+    )))
 }
 
 impl AppService {