Retire pre-provenance onboard lock compatibility

## Context

PR #10845 retains parsing and diagnostics for the exact pre-provenance onboard lock format (`pid`, `startedAt`, and `command`). New lock publication writes host, PID namespace, and process-start provenance instead.

Because the legacy record does not prove which host or PID namespace created it, NemoClaw treats it as held even when that PID is absent locally. Recovery requires operator resolution; local PID absence alone never authorizes reclamation on a shared state filesystem.

## Retirement exit criteria

Remove the legacy parser/diagnostic branch and its focused tests once the documented minimum supported direct-upgrade source release is at or after the first release containing #10845. At that point every supported source release writes provenance fields, so no supported version can create the legacy format.

If NemoClaw does not yet publish a minimum supported direct-upgrade source version, keep this issue open until that policy and cutoff are documented.

Start with PR #10845, then locate the legacy parser/diagnostic branch and its focused tests. Verify whether the minimum supported direct-upgrade source release and cutoff are documented; done means that policy is documented at or after the first provenance-writing release, and the legacy branch and tests are removed.

Written by the indexing model from the issue text.