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/cli/package.json

@@ -57,9 +57,9 @@
     }
   },
   "devDependencies": {
-    "@kb/core": "workspace:*",
-    "@kb/dashboard": "workspace:*",
-    "@kb/engine": "workspace:*",
+    "@fusion/core": "workspace:*",
+    "@fusion/dashboard": "workspace:*",
+    "@fusion/engine": "workspace:*",
     "@sinclair/typebox": "^0.34.0",
     "@types/node": "^22.0.0",
     "@vitest/coverage-v8": "^3.1.0",