Add CDN-ready headers, ROADMAP, fold runtime into mizan-react

CDN headers on context GETs (Edge-ready):
- Cache-Control: public, max-age=0, stale-while-revalidate=300
- Vary: Authorization, Cookie
- Deterministic JSON (sorted keys) for consistent cache keys
- Error responses: Cache-Control: no-store
- Mutation POSTs: Cache-Control: no-store

ROADMAP.md documents v1 deliverables and Mizan Cloud (Edge, Render,
Deploy) as closed-source products built on the open-source protocol.

mizan-runtime folded into mizan-react/src/runtime/ — framework-agnostic
split deferred until a second frontend adapter exists.

268 Django + 33 React tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/mizan-runtime/package.json

@@ -1,12 +0,0 @@
-{
-  "name": "@mizan/runtime",
-  "version": "0.1.0",
-  "description": "Mizan client state engine — framework-agnostic context registry, invalidation, and fetch.",
-  "type": "module",
-  "main": "index.ts",
-  "types": "index.ts",
-  "exports": {
-    ".": "./index.ts"
-  },
-  "license": "MIT"
-}