feat(KB-330): rename internal packages from @kb/* to @fusion/*

- Rename @kb/core, @kb/dashboard, @kb/engine to @fusion/* namespace
- Update all import statements across 143+ files to use new package names
- Update workspace dependencies and root package.json references
- Fix bundler configurations (tsup, vite) for new package names
- Update test files and fix typecheck issues
- Add changeset file documenting the package rename

packages/dashboard/app/components/ActivityLogModal.tsx

@@ -1,7 +1,7 @@
 import { useState, useEffect, useCallback, useRef } from "react";
 import { X, History, Trash2, Filter, RefreshCw, CheckCircle, XCircle, ArrowRight, Plus, Settings, AlertCircle, Loader2 } from "lucide-react";
 import { fetchActivityLog, clearActivityLog, type ActivityLogEntry, type ActivityEventType } from "../api";
-import type { Task } from "@kb/core";
+import type { Task } from "@fusion/core";
 
 interface ActivityLogModalProps {
   isOpen: boolean;