feat(FN-3257): sort board tasks by priority then task number instead of mov

Replaced the board's task ordering from time-based (`columnMovedAt`/`createdAt`) to a priority-then-task-number sort, inlining previously external priority helpers to fix Vite bundling. Tests were updated in `Board.test.tsx` to match the new sort semantics and `ChatView.test.tsx` keyboard tests were

Fusion-Task-Id: FN-3257

docs/architecture.md

@@ -492,6 +492,7 @@ Key server capabilities:
 - App entry: `packages/dashboard/app/main.tsx`
 - Root composition: `packages/dashboard/app/App.tsx`
 - Core board components: `Board.tsx`, `Column.tsx`, `TaskCard.tsx`, `TaskDetailModal.tsx`, `ListView.tsx`
+- **Board column ordering**: task cards within each board column are sorted by priority descending (`urgent` → `high` → `normal` → `low`) and then by numeric task ID ascending (lower ID first). Missing or invalid priority values normalize to `normal`. In the `in-review` column, tasks with `status === "merging"` or `status === "merging-pr"` are pinned above non-merging tasks, with the priority-then-ID ordering applied within each pinned/non-pinned group.
 - Task detail surface is shared through `TaskDetailContent` (exported from `TaskDetailModal.tsx`): desktop/tablet `ListView` renders it inline in the split right pane, while mobile and non-list entry points continue using `TaskDetailModal`.
 - In desktop split mode, `ListView` now uses a compact sidebar-first control layout (count/actions/summary chips + collapsible "View options" panel) to keep list controls dense alongside the inline detail pane; mobile keeps the card-first flow with a toolbar "View options" entry point for the same visibility/filter toggles.
 - Chat system UI: `ChatView.tsx`, `QuickChatFAB.tsx`