Report the effective archived state in the settings context

What does this MR do and why?

Govern::PolicyEngine::SettingsContext reported the stored archived column in the evaluation context. That value is not the state GitLab presents: it ignores an archived ancestor group, and it still counts a project that only awaits deletion. A scope rule such as archived == false then kept matching a project the user already sees as archived through its group, so the policy kept firing on something the user cannot change.

This reports project.self_or_ancestors_archived? instead, which counts an archived ancestor and excludes a project awaiting deletion, and preloads the namespace inherited-settings association so batch evaluation keeps the loaded-association fast path. The class comment now separates the derived scope keys (archived, groups) from the project's own stored settings.

The context schema in !261559 (merged) needs no change: it describes the key as "Whether the project is archived", and the effective state matches that description. The whole feature stays behind the policy_store_experiment_enabled setting, the security_policies_v2 flag, and the security_orchestration_policies license, so no changelog entry.

Merge plan (nested = depends on parent, siblings = parallel)

• !261560 (merged) evaluation service
  • !261838 settings fence
  • !261561 drift workers
  • !261562 conflict check
    • !261837 set_setting write-back
      • !264545 cross-trigger E2E (also needs fence, drift workers)
• !262405 effective archived state (this MR)

References

• Follow-up to !261559 (merged), raised in !261559 (comment 4012898821)
• Resolves https://gitlab.com/gitlab-org/gitlab/-/work_items/633807

Screenshots or screen recordings

Backend-only change, no UI.

Before	After

How to set up and validate locally

1. Build the context for a project whose ancestor group is archived:

   project = Project.find(id) # inside an archived group
   Govern::PolicyEngine::SettingsContext
     .build(project: project, trigger: 'project_settings_change_requested')
     .dig('project', 'archived')
   # => true  (was false before this change)

2. Run the specs:

   bin/rspec ee/spec/lib/govern/policy_engine/settings_context_spec.rb

MR acceptance checklist

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