refactor: add print_structured() shared helper, migrate CLI console output

[ProtocolWarden]

Summary

• Rich console structured-output printing was hand-rolled 4 inconsistent ways across 9 CLI files — some bypassed Console entirely via typer.echo(json.dumps(...)), others routed through Console but printed a pre-serialized string, losing syntax highlighting.
• Adds print_structured(console, output, *, sort_keys=False) in the new operations_center.cli_output module, normalizing dict/BaseModel/dataclass payloads and always rendering via console.print_json(...).
• Migrates all 15 in-scope call sites across audit, calibration, governance, run_show, worker_backend_probe, worker_backend_status, observer, run_memory, and artifact_index. Two call sites are deliberately left unmigrated — a truncated raw-content dump (artifact_index/cli.py get-artifact --print-content) and a formatter-routed combined-output branch (observer/cli.py query-flaky-tests) — since print_structured has no equivalent for their extra semantics.

Test plan

• tests/unit/test_cli_output.py — 22 tests, 100% line/branch coverage on the new helper
• Updated existing CLI tests whose mocks no longer matched the helper's BaseModel/dataclass type-dispatch
• ruff check . — 0 violations; ruff format --check — clean on all touched files
• Full suite: 10298 passed, 6 failed (all pre-existing sandbox/timing failures, reproduced identically on the unmodified branch tip), 21 skipped, 2 xfailed — zero new failures

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