test(oauth-client): rename sub-stage snapshots to reflect default-run behavior
The `*_all_pass_snapshot` names from the final-review coverage fix were
misleading: the current sub-stage driver reuses state across per-flow runs
so only a subset of checks actually pass, and the snapshots capture
several SpecViolations. Rename to `*_default_run_snapshot` and add doc
comments explaining the state-reuse caveat. AC8.7 ID coverage is
unchanged.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>