FN-7661: expose removeLineageReferences on fn_task_archive/fn_task_delete

Fixes fn_task_archive and fn_task_delete rejecting tasks still referenced as a lineage parent, with no tool-exposed way to clear that reference.

- Add optional removeLineageReferences boolean param to fn_task_archive and fn_task_delete tool schemas, forwarded to store.archiveTask/store.deleteTask
- Update tool descriptions and prompt guidelines to advertise the recovery path (removeLineageReferences:true) when a lineage-parent block occurs
- Add task-lineage-unlink.test.ts covering the new parameter behavior
- Document the change in docs/storage.md
- Add changeset (@runfusion/fusion minor, category: fix)

Files changed:
 .changeset/fn-7661-lineage-unlink-tools.md         |   7 +
 docs/storage.md                                    |   1 +
 packages/cli/src/__tests__/task-lineage-unlink.test.ts | 199 +++++++++++++++++++++
 packages/cli/src/extension.ts                      |  28 ++-
 4 files changed, 232 insertions(+), 3 deletions(-)

Fusion-Task-Id: FN-7661

Fusion-Task-Lineage: 414c046c-43df-4995-85a5-ff00b345de50

Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai>

docs/storage.md

@@ -55,6 +55,7 @@
 - Gate boundary: soft-deleted children and archived-column children do **not** block parent removal; only live non-archived children block.
 - `cleanupArchivedTasks` intentionally tolerates dangling lineage pointers in historical/archive cleanup flows; it does not run lineage rewrites.
 - For forensic reads, soft-deleted parents remain accessible through `readTaskFromDb(id, { includeDeleted: true })`.
+- Agent-facing tool layer (FN-7661): the `fn_task_archive` and `fn_task_delete` pi/CLI tools (`packages/cli/src/extension.ts`) both accept an optional `removeLineageReferences` boolean and forward it to `store.archiveTask` / `store.deleteTask`, so an agent that hits `TaskHasLineageChildrenError` can retry with `{ removeLineageReferences: true }` to clear the block — matching the recovery path the error message already advertises.
 
 ### Documents under soft-deleted tasks (FN-5140)