Adds task lineage commit associations: a new API route stores and exposes which commits belong to which task, the `TaskChangesTab` surfaces these lineage links visually, and documentation covers the reconciliation model. Includes comprehensive tests for both the route and component.
Fusion-Task-Id: FN-3998
Adds task lineage storage infrastructure (FN-3990 Step 2), introducing a dedicated `task-lineage.ts` module and related types to track task identity and association relationships, with corresponding database schema and store support plus tests and documentation for the lineage reconciliation process
Fusion-Task-Id: FN-3990
