fix(jina-reader): recover after transient errors and use JSON POST API

Clear stale provider error code and account lock after a successful web
fetch (the core fetch handler never consumed the onRequestSuccess
callback), switch Jina Reader to its documented JSON POST request, and
parse the Title: metadata line before falling back to a Markdown heading.

src/sse/handlers/fetch.js

@@ -195,13 +195,11 @@ async function handleSingleProviderFetch(body, providerInput, request, apiKey, s
           providerSpecificData: newCreds.providerSpecificData,
           testStatus: "active"
         });
-      },
-      onRequestSuccess: async () => {
-        await clearAccountError(credentials.connectionId, credentials);
       }
     });
 
     if (result.success) {
+      await clearAccountError(credentials.connectionId, credentials);
       return new Response(JSON.stringify(result.data), {
         headers: { "Content-Type": "application/json", "Access-Control-Allow-Origin": "*" }
       });