README: add Python reference server, cross-link from Node

Author: MHWing

README.md

@@ -38,6 +38,14 @@ A runnable, in-memory implementation of OCAS in Node.js. Start it with `npm inst
 
 ---
 
+### [ocas-reference-python](./ocas-reference-python/), OCAS reference server (Python)
+
+The same reference server, in Python with FastAPI. Identical behaviour and rules to the Node version, so you can see the spec is genuinely portable across stacks. Start it with `uvicorn ocas.server:app --reload` and FastAPI even serves its own interactive docs at `/docs`. Ships with a pytest conformance suite. Built for learning and conformance testing, not production.
+
+📁 [`./ocas-reference-python/`](./ocas-reference-python/) · 🟢 `uvicorn` · ✅ tested · *Implements OCAS draft v0.1*
+
+---
+
 ## How to get involved
 
 - **Adopt a spec.** The fastest way to help is to implement one of our standards in a real product and tell us what broke. Adoption stories beat theoretical critique.

ocas-reference-node/README.md

@@ -98,6 +98,6 @@ It's deliberately small and readable. If you want to build a real OCAS server, t
 
 ## Where this fits
 
-This is one implementation of OCAS. The spec is the source of truth; if this server and the spec ever disagree, the spec wins (and please [open an issue](https://github.com/the-foundation-stack/Foundation/issues)). Implementations in other languages — Python, Go, PHP, Ruby — are very welcome as contributions.
+This is one implementation of OCAS. The spec is the source of truth; if this server and the spec ever disagree, the spec wins (and please [open an issue](https://github.com/the-foundation-stack/Foundation/issues)). There's also a [Python reference server](../ocas-reference-python/) with identical behaviour. Implementations in further languages (Go, PHP, Ruby, Rust) are very welcome as contributions.
 
 Licensed Apache 2.0, same as the rest of The Foundation.