Follow-up to: #3582504 _**NOTE: Before working on this issue, verify it's still relevant and makes sense.**_ **Description:** Add tools for keeping context relevant and fresh over time. This includes detecting stale context, validating assembled context before injection, and improving scoring based on task intent. **Includes:** - Full `2.1` Context staleness detection - `2.2` Context assembly validation - `4.3` Task/intent-aware scoring **Scope:** - Add staleness detection using reserved fields such as `review_by` and `auto_expire`. - Add warnings or filters for expired/stale context. - Add validation for assembled context before it is returned. - Add task/intent-aware relevance metadata and scoring. - Provide admin UI affordances where needed. **Acceptance criteria:** - Stale context can be identified without breaking existing items. - Validation failures are observable and fail safely. - Task relevance scoring is deterministic and testable. - Admins can understand why context is stale, invalid, or low relevance. [x] AI Assisted Issue