Implement consent renewal, revocation, and processing-state enforcement

[llinsss]

Problem

Consent is validated only when a profile is first created. After that, there is no supported way to revoke consent, record a superseding policy version, distinguish active from historical consent, or block processing after withdrawal. Deletion exists, but deletion alone is not an auditable consent lifecycle and a later request with new metadata can recreate the profile.

For a system handling children's learning data, every processing path should enforce an explicit current consent state.

Proposed change

• Model consent as append-only events (granted, renewed, revoked) with actor, method, policy version, effective time, and server receipt time.
• Add guardian-authorized endpoints to inspect consent status, renew it, and revoke it.
• On revocation, atomically block new attempts, diagnostics, recommendations, stories, reports, and AI calls before optionally starting deletion according to a documented policy.
• Define policy-version behavior: whether a version change requires renewal, the grace period if any, and the response returned while renewal is required.
• Keep the minimum audit evidence necessary after deletion only if legally justified and documented; otherwise purge it with the student data.
• Include consent history/status in portable exports and retention logic.
• Document that identity/authority verification belongs to the upstream guardian portal while ensuring this API cannot bypass the resulting state.

Acceptance criteria

• Revoked or renewal-required profiles cannot be processed by any student-data endpoint.
• Revocation is idempotent and cannot race with an attempt/diagnostic write to recreate active data.
• Consent history has immutable timestamps and policy versions, and is present in exports.
• Re-consent follows a documented flow and never mutates prior audit events.
• Tests cover grant, renew, revoke, repeated revoke, processing denial, deletion, export, and retention interactions.
• PRIVACY.md and API docs describe the lifecycle and remaining legal/product decisions.

Relevant code

• agent/profiler.py (consent validation/profile creation)
• agent/privacy.py
• api/routes.py
• PRIVACY.md

[johnvon1112]

Hi, I'd like to pick up this issue. Kindly assign

[grantfox-oss]

🦊 GrantFox — @johnvon1112 has been assigned to this issue as part of the Third Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #23)
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