Add design document; Cross reference from existing docs, and add a section on maglevt

README.md

@@ -2,7 +2,7 @@
 
 Health checker, gRPC control plane, CLI, and web dashboard for the VPP
 `lb` (load-balancer) plugin. Runs as a set of three binaries under one
-Debian package:
+Debian package, plus an out-of-band tester built alongside:
 
 - **`maglevd`** — the long-running health-checker daemon. Probes backends
   (HTTP, TCP, ICMP), tracks their aggregate state, programs the VPP
@@ -14,6 +14,12 @@ Debian package:
   SolidJS Single-Page-App; connects to one or more maglevds over gRPC and
   serves a live HTTP view (read-only `/view/` and optional basic-auth
   `/admin/` with mutating commands).
+- **`maglevt`** — optional out-of-band VIP probe TUI. Reads a
+  `maglev.yaml` and hits each frontend on a live HTTP path, reporting
+  latency and a configurable response-header tally so operators can see
+  failover as it happens. Does not talk gRPC; useful for validating a
+  `maglevd` restart end-to-end from a client perspective. Built by
+  `make` but not installed by the Debian package.
 
 ## Build and install
 
@@ -94,6 +100,9 @@ deployments.
 
 ## Documentation
 
+- [docs/design.md](docs/design.md) — architecture, components, and
+  numbered functional / non-functional requirements. Start here if
+  you want the big picture before diving into the code.
 - A minimal configuration file in
   [debian/maglev.yaml](debian/maglev.yaml) shows every knob.
 - [docs/user-guide.md](docs/user-guide.md) — flags, signals, and