FN-5792: fix GitHub auto-close reconciliation for soft-deleted tasks

Ensure GitHub issue auto-close reconciliation still processes soft-deleted and archived tracked tasks after restart.

- Add pagination-aware reconcile scanning in core store with combined deleted+archived coverage and hasMore metadata.
- Update dashboard GitHub tracking reconciler and route handling to consume paged reconcile batches safely.
- Expand reconcile tests (core + dashboard) with restart/periodic sweep and source-issue scenarios to lock behavior.
- Add release changeset and dashboard guide note for the reconciliation sweep behavior.

Files changed:
 .changeset/fn-5792-github-tracking-sweep.md        |   5 +
 docs/dashboard-guide.md                            |   1 +
 .../store-github-tracking-reconcile.test.ts        |  45 ++++++++-
 packages/core/src/store.ts                         |  32 ++++--
 .../github-source-issue-reconciler.test.ts         |  22 ++--
 ...ithub-tracking-periodic-reconcile-sweep.test.ts |  90 +++++++++++++++++
 .../__tests__/github-tracking-reconciler.test.ts   | 111 +++++----------------
 .../dashboard/src/github-tracking-reconciler.ts    |  19 ++--
 .../dashboard/src/routes/register-git-github.ts    |  57 +++++++++--
 9 files changed, 257 insertions(+), 125 deletions(-)

Fusion-Task-Id: FN-5792

Fusion-Task-Lineage: 259f07cf-3470-47c7-b47a-86d212d44d52

docs/dashboard-guide.md

@@ -587,6 +587,7 @@ Inspect task definition, logs, review feedback, comments, documents, workflow ou
 - Task metadata also shows compact `Created` / `Updated` timestamps: recent values render as relative time (`just now`, `Xm`, `Xh`, `Xd`) and older values switch to short month/day dates; these stay grouped on one row across desktop and mobile widths for a compact metadata layout.
 - Eligible existing tasks (triage, todo, in-progress, in-review) expose a **GitHub tracking** section directly in Task Detail, even when tracking is currently disabled.
 - The GitHub tracking section now defaults to a compact summary row; use the disclosure arrow to expand linked-issue details plus tracking edit controls.
+- Backstop reconciliation runs every 15 minutes to close tracked GitHub issues for soft-deleted and archived tasks even after restart; the sweep is paginated so large archive backlogs are eventually drained.
 - In shared task edit/create forms, GitHub Tracking appears at the bottom of **More options**, after **Workflow Steps**.
 - From this section you can explicitly enable/disable tracking and manage a per-task repo override (`owner/repo`). Clearing the override saves `null` and falls back to project/global defaults.
 - In `in-review`, pull-request controls/status (including stall badges) are in a dedicated **Pull Request** tab instead of the Definition tab.