fix(toolkit): contract-address --untagged handling and stdout cleanliness (#1402)

[m2ux]

Summary

Align midnight-node-toolkit contract-address help output with runtime behaviour. Hide the deprecated --untagged flag from --help, move its deprecation warning from eprintln! to log::warn! so it participates in the toolkit's logging contract (RUST_LOG, --quiet, --verbose), and reject --tagged --untagged at parse time via conflicts_with. Success path now emits empty stderr, matching the show-address sister-command pattern.

🐛 Issue 📐 Engineering

Jira: PM-19934

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Motivation

The toolkit contract-address command advertises an --untagged option in its --help output, but the implementation already moved to untagged-by-default. Passing --untagged emits Warning: \--untagged` flag is deprecated (now default)viaeprintln!on stderr while still returning the same address--no-flagwould have returned. Help text and runtime behaviour disagree, and the warning channel bypasses the toolkit'stracing_subscriberlogging contract — so it is not suppressible viaRUST_LOG, not gated by --quiet`, and does not pick up the standard log prefix. Downstream consumers that merge stdout/stderr observe the warning mixed in with the address.

The sister command show-address already handles its own deprecated alias (--unshielded-user-address-untagged) cleanly by pairing conflicts_with declarations on the current and deprecated flags and emitting log::warn! only when the deprecated alias is selected. This PR brings contract-address into alignment with that pattern.

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Changes

Implementation (Path A — backward-compatible cleanup):

• Mark ContractAddressArgs::untagged with hide = true so it disappears from --help while remaining parseable for existing callers
• Add conflicts_with declarations between --tagged and --untagged so passing both is a clap parse error rather than a silent "tagged wins" outcome
• Replace eprintln! deprecation warning with log::warn! matching the show-address idiom; the warning is now suppressible via RUST_LOG=error and picks up the standard toolkit log prefix
• Rewrite the doc-comment on the deprecated field to explicitly state "kept for backward compatibility; will be removed in a future major version"
• Add trycmd snapshot tests under util/toolkit/tests/cmd/ covering: (a) --help does not advertise --untagged, (b) success path emits empty stderr, (c) --untagged alone still works but logs a warning, (d) --tagged --untagged is rejected by clap
• Add changes/toolkit/changed/contract-address-untagged-flag-cleanup.md change-file entry

The --tagged alternative output mode and the default-no-flag output are unchanged. Path B (full flag removal) was considered and rejected for this Low-priority UX bug on external-caller-risk grounds; see the linked Engineering README for the design rationale.

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📌 Submission Checklist

• Changes are backward-compatible (or flagged if breaking)
• Pull request description explains why the change is needed
• Self-reviewed the diff
• I have included a change file, or skipped for this reason: [reason]
• If the changes introduce a new feature, I have bumped the node minor version
• Update documentation (if relevant)
• No new todos introduced

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🔱 Fork Strategy

• Node Runtime Update
• Node Client Update
• Other
• N/A

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🗹 TODO before merging

• Ready for review

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Closes #1402