node: add safe constructors

[malsomesh9]

Summary

• add explicit error-returning node constructors (NewFromConfPathE, NewE, NewWithConfPathE)
• keep the legacy panicing constructors as compatibility wrappers
• adopt the safe constructor path in benchmark setup so bad config returns an error instead of crashing the process

Why

#183 calls out panic-heavy API paths. The node construction flow was one of the clearest user-facing cases: bad config could trigger a panic during setup. This PR introduces safe alternatives without breaking existing callers and starts moving internal code onto the error-returning path.

Testing

• go test ./pkg/node
• go test ./node
• go test ./integration/benchmark/node

Refs #183

[github-actions]

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[github-actions]

Hi @malsomesh9 👋 — the recent merge of PR #1416 has introduced a merge conflict in this PR. Please resolve the merge conflict so that this PR can be reviewed again. Thank you!