AgentPod 089: Add evidence retention policy controls

[EfeDurmaz16]

Objective

Complete issue 89 from the AgentPod productization plan: Add evidence retention policy controls.

Why This Matters

AgentPod is the primary product surface. This work moves Agentbox from a collection of runtime/control features toward a credible governed execution product with honest provider boundaries.

Scope

• Epic: Epic 9: Evidence, FIDES, and AGIT
• Area: evidence/storage
• Priority: P2
• Expected PR boundary: config and cleanup behavior

Out of scope: fake provider support, broad rewrites unrelated to this issue, or claims not backed by the verification gate.

Acceptance Criteria

• Behavior, documentation, or contract described by the issue exists.
• Tests, smoke checks, or docs validation cover the change where practical.
• Verification gate passes: retention dry-run lists deletions and never removes unverified active session data.
• Provider/support level remains honest; descriptor-only and prototype surfaces are not presented as shipped.

Verification

retention dry-run lists deletions and never removes unverified active session data.

Suggested PR Boundary

config and cleanup behavior

Source

Derived from docs/agentpod-productization-100-issues.md at commit 33d44f8.