feat(network): add structured failure traces to fail fulfillment

[fakedev9999]

Summary

Adds an optional structured failure trace field to FailFulfillmentRequestBody so open-source prover clusters can send useful failure context when reporting failed fulfillments.

This is the producer-side wire contract for network-services PR #1191. The field number intentionally matches the receive-side proto there:

• FailFulfillmentRequestBody.error_trace = 4

The field carries bounded, sanitized UTF-8 JSON bytes. Consumers may omit it when no useful context is available.

Why

External prover operators run the open-source sp1-cluster fulfiller, which depends on this repo's spn-network-types. Today that fulfiller can reduce cluster failure details to a coarse ProofRequestError, but it has no wire field for the original structured context. As a result, mainnet SPN requests can end up with opaque failures like Unknown Error.

This PR gives the fulfiller a compatible field and helper for constructing the trace from cluster extra_data.

What Changed

• Adds optional bytes error_trace = 4 to FailFulfillmentRequestBody.
• Regenerates the Rust network types.
• Adds spn_network_types::error_trace, including:
  • ErrorTrace::from_cluster_extra_data(...)
  • sanitization/redaction
  • per-field and total size bounds
  • wire serialization helpers
• Handles the real cluster proving-failure shape where task_type is serialized as a string enum name, for example:
  • {"proving_failure":{"reason":"GPU OOM","task_type":"ProveShard"}}
• Documents the manual sync requirement with network-services PR #1191.

Scope

This PR only adds the wire contract and producer-side helper in network.

The follow-up sp1-cluster PR will:

• pin to this network rev
• wire bin/fulfiller to convert proof_requests.extra_data into error_trace
• send it on fail_fulfillment

The receive/store side is handled separately in network-services PR #1191.

Validation

• cargo build --features network
• cargo test -p spn-network-types error_trace --lib → 44 passed
• cargo +nightly fmt --check → clean
• cargo clippy --features network -D warnings → clean
• git diff --check → clean

[0xernesto]

Looks like you need to add error_trace: None to make CI pass