Flatten to three packages + extract mizan-runtime

packages/
  mizan-runtime/   Framework-agnostic state engine (~150 lines)
                   Context registry, batched invalidation, fetch primitives
  mizan-django/    Django server adapter (was packages/mizan-rpc/adapters/django/)
                   Codegen moved to mizan-django/generate/
  mizan-react/     React adapter (was packages/mizan-csr/adapters/react/)

Removed premature abstractions: mizan-ast, mizan-schema, mizan-rpc,
mizan-csr, mizan-ssr stub packages. The actual architecture is three
concrete packages, not five abstract layers.

mizan-runtime implements the v1 spec: registerContext with params,
scoped invalidation via microtask batching, server-driven invalidation
from mutation responses, mizanFetch for context bundles, mizanCall for
mutations.

264 Django + 33 React tests pass.

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

packages/mizan-runtime/index.ts

@@ -0,0 +1,145 @@
+/**
+ * Mizan Runtime — The client state engine.
+ *
+ * Framework-agnostic. React, Vue, Svelte, Solid — all wrap this.
+ *
+ * Three concerns:
+ * 1. Context registry — mounted providers register here for invalidation
+ * 2. Invalidation — batched via microtask, supports scoped params
+ * 3. Fetch — mizanFetch (GET context bundles) + mizanCall (POST mutations)
+ */
+
+// === Types ===
+
+export class MizanError extends Error {
+    constructor(public status: number, public body: string) {
+        super(`Mizan call failed (${status})`)
+    }
+}
+
+export type RefetchFn = () => void
+type ParamKey = string // JSON.stringify of params
+
+interface ContextEntry {
+    params: Record<string, any>
+    refetch: RefetchFn
+}
+
+// === Configuration ===
+
+let config = {
+    baseUrl: '/api/mizan',
+    getHeaders: (): Record<string, string> => ({}),
+}
+
+export function configure(opts: Partial<typeof config>) {
+    Object.assign(config, opts)
+}
+
+// === Context Registry ===
+// Mounted context providers register here. Unmounted ones deregister.
+
+const contexts: Map<string, Map<ParamKey, ContextEntry>> = new Map()
+
+export function registerContext(
+    name: string,
+    params: Record<string, any>,
+    refetch: RefetchFn,
+): () => void {
+    if (!contexts.has(name)) contexts.set(name, new Map())
+    const key = JSON.stringify(params)
+    contexts.get(name)!.set(key, { params, refetch })
+    return () => contexts.get(name)!.delete(key)
+}
+
+// === Invalidation ===
+// Batched via microtask. Multiple invalidations in the same tick coalesce.
+
+const pending: Set<string> = new Set()
+const pendingScoped: Map<string, Record<string, any>> = new Map()
+let scheduled = false
+
+export function invalidate(context: string, params?: Record<string, any>) {
+    if (params) {
+        pendingScoped.set(context, params)
+    } else {
+        pending.add(context)
+    }
+    if (!scheduled) {
+        scheduled = true
+        queueMicrotask(flush)
+    }
+}
+
+function flush() {
+    // Broad invalidations — refetch all instances of context
+    for (const name of pending) {
+        const entries = contexts.get(name)
+        if (entries) entries.forEach(entry => entry.refetch())
+    }
+
+    // Scoped invalidations — refetch only matching params
+    for (const [name, params] of pendingScoped) {
+        if (pending.has(name)) continue // already refetched all
+        const entries = contexts.get(name)
+        if (!entries) continue
+        const key = JSON.stringify(params)
+        const entry = entries.get(key)
+        if (entry) entry.refetch()
+    }
+
+    pending.clear()
+    pendingScoped.clear()
+    scheduled = false
+}
+
+// === Fetch ===
+
+export async function mizanFetch(
+    contextName: string,
+    params?: Record<string, any>,
+): Promise<any> {
+    const url = new URL(`${config.baseUrl}/ctx/${contextName}/`, globalThis.location?.origin ?? 'http://localhost')
+    if (params) {
+        for (const [k, v] of Object.entries(params)) {
+            url.searchParams.set(k, String(v))
+        }
+    }
+    const res = await fetch(url.toString(), {
+        headers: { ...config.getHeaders(), 'Accept': 'application/json' },
+        credentials: 'same-origin',
+    })
+    if (!res.ok) throw new MizanError(res.status, await res.text())
+    return res.json()
+}
+
+export async function mizanCall(
+    functionName: string,
+    args: Record<string, any>,
+): Promise<any> {
+    const res = await fetch(`${config.baseUrl}/call/`, {
+        method: 'POST',
+        headers: {
+            ...config.getHeaders(),
+            'Content-Type': 'application/json',
+        },
+        credentials: 'same-origin',
+        body: JSON.stringify({ function: functionName, args }),
+    })
+    if (!res.ok) throw new MizanError(res.status, await res.text())
+
+    const data = await res.json()
+
+    // Server-driven invalidation
+    if (data.invalidate) {
+        for (const entry of data.invalidate) {
+            if (typeof entry === 'string') {
+                invalidate(entry)
+            } else {
+                invalidate(entry.context, entry.params)
+            }
+        }
+    }
+
+    return data.result
+}