fix: propagate pending user operation RPC errors

[realmehmetali]

Summary

• detect JSON-RPC errors returned by eth_getUserOperationByHash
• propagate them instead of reporting the payment as not_found
• add regression coverage for the error and telemetry paths

Why

When the receipt lookup returned null, the follow-up user-operation lookup ignored its JSON-RPC error field. A bundler failure could therefore be misreported as a missing operation.

Agent impact

Autonomous agents need to distinguish a genuinely absent user operation from an RPC failure before deciding whether to retry, alert, or advance a payment workflow. Accurate failure semantics are foundational for safe agent-run payment loops.

Validation

• focused payment-status suite: 20 tests passed
• package typecheck
• package build
• Biome check on changed files

[cb-heimdall]

🟡 Heimdall Review Status

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