fix(FN-2055): harden node test utilities and import resolution

- Convert seed-sample-nodes into a test-only helper and remove direct execution against the real central database
- Replace private-looking host examples with RFC 5737 test-net addresses in node connection docs and ConnectNodeModal expectations
- Add Vitest aliases for @fusion/core and @fusion/engine to stabilize cross-package test imports
- Load AgentReflectionService via local engine source path in in-process runtime to avoid alias resolution failures

packages/dashboard/app/components/ConnectNodeModal.tsx

@@ -198,7 +198,7 @@ export function ConnectNodeModal({ open, onClose, onConnected, addToast, onSubmi
               type="text"
               value={host}
               onChange={(event) => setHost(event.target.value)}
-              placeholder="192.168.1.100 or my-server.local"
+              placeholder="192.0.2.10 or my-server.local"
               disabled={isSubmitting}
               aria-invalid={Boolean(errors.host)}
             />