fix(consensus): reject execution WebSocket endpoint with IPC

[Kewe63]

Summary

Fixes #338

Reject consensus CLI configurations that combine IPC transport options with --execution-ws-endpoint.

The WebSocket endpoint is an RPC transport option, but it was omitted from the IPC/RPC conflict check. As a result, a complete IPC configuration could be accepted together with an execution WebSocket endpoint, after which the IPC configuration took precedence and the explicitly supplied WebSocket endpoint was silently ignored.

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Problem

StartCmd::validate() classifies these fields as RPC options when checking for conflicts with IPC:

• --eth-rpc-endpoint
• --execution-endpoint
• --execution-jwt

However, it omitted:

• --execution-ws-endpoint

This was inconsistent with the later uses_rpc_transport check, which already treats execution_ws_endpoint as an RPC transport option.

When both IPC sockets and --execution-ws-endpoint were configured:

1. CLI validation succeeded.
2. StartConfig::engine_config() selected EngineConfig::Ipc.
3. The supplied WebSocket endpoint was not used.
4. The node could start with an explicit configuration value silently ignored.

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Changes

• Include execution_ws_endpoint in the RPC option set used by the IPC/RPC conflict validation.
• Include --execution-ws-endpoint in the conflict error's list of RPC options.
• Add a regression test covering a complete IPC configuration combined with an explicit execution WebSocket endpoint.

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Regression Coverage

The new test configures:

--eth-socket /tmp/reth.ipc
--execution-socket /tmp/reth-auth.ipc
--execution-ws-endpoint

and verifies that:

• validation rejects the configuration;
• the error reports an IPC/RPC conflict;
• the error identifies --execution-ws-endpoint as an RPC option.

The regression test was confirmed to fail against the previous implementation before the validation fix was applied.

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How to Test

cargo +1.94.0 test
-p arc-node-consensus-cli
validate_err_when_mixing_ipc_and_execution_ws_endpoint
-- --nocapture

Result:

1 passed; 0 failed

Full affected package:

cargo +1.94.0 test -p arc-node-consensus-cli

Result:

89 passed; 0 failed

Additional checks:

cargo +1.94.0 fmt -p arc-node-consensus-cli -- --check
cargo +1.94.0 clippy -p arc-node-consensus-cli --all-targets -- -D warnings
git diff --check

All checks passed.

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Scope and Risk

This is limited to CLI validation and its regression coverage.

It does not change:

• IPC connection behavior;
• RPC connection behavior;
• WebSocket endpoint derivation;
• EngineConfig construction;
• consensus or protocol behavior.

Existing valid IPC-only and RPC-only configurations are unaffected.

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Duplicate Check

Open and closed issues and pull requests were searched using the affected flag names, transport combinations, and conflict message. No direct duplicate or existing implementation was found.

Issue #294 and PR #295 concern separated-host deprecation wording and do not address this validation gap.

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Checklist

• The bug was reproduced on current main.
• A regression test was added and proven to fail before the fix.
• The implementation is limited to the affected validation path.
• Focused and package tests pass.
• Formatting and Clippy checks pass.
• No protocol, persistence, API, or dependency changes are included.
• The change was reviewed independently.
• Follows Conventional Commits

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Impact

Type: 🐛 Bug fix
Fixes: #338