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-django/tests/models.py

@@ -0,0 +1,142 @@
+from django.contrib.auth.models import (
+    AbstractBaseUser,
+    BaseUserManager,
+    PermissionsMixin,
+)
+from django.db import models
+
+
+class EmailUserManager(BaseUserManager):
+    """Custom user manager using email as the unique identifier."""
+
+    def create_user(self, email, password=None, **extra_fields):
+        if not email:
+            raise ValueError("Email is required")
+        email = self.normalize_email(email)
+        user = self.model(email=email, **extra_fields)
+        user.set_password(password)
+        user.save(using=self._db)
+        return user
+
+    def create_superuser(self, email, password=None, **extra_fields):
+        extra_fields.setdefault("is_staff", True)
+        extra_fields.setdefault("is_superuser", True)
+        return self.create_user(email, password, **extra_fields)
+
+
+class EmailUser(AbstractBaseUser, PermissionsMixin):
+    """Minimal user model with email as USERNAME_FIELD.
+
+    Matches the calling convention used in mizan's test suite:
+        User.objects.create_user(email="...", password="...", is_staff=True)
+    """
+
+    email = models.EmailField(unique=True)
+    is_staff = models.BooleanField(default=False)
+    is_active = models.BooleanField(default=True)
+
+    objects = EmailUserManager()
+
+    USERNAME_FIELD = "email"
+    REQUIRED_FIELDS = []
+
+    class Meta:
+        app_label = "tests"
+
+
+# ─── Shape test models ──────────────────────────────────────────────────────
+
+import uuid
+
+
+class TimestampMixin(models.Model):
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        abstract = True
+
+
+class Publisher(TimestampMixin):
+    name = models.CharField(max_length=200)
+    country = models.CharField(max_length=100, default="")
+
+    class Meta:
+        app_label = "tests"
+
+
+class Author(TimestampMixin):
+    name = models.CharField(max_length=200)
+    bio = models.TextField(default="")
+    publisher = models.ForeignKey(
+        Publisher, on_delete=models.CASCADE, related_name="authors"
+    )
+    mentor = models.ForeignKey(
+        "self", on_delete=models.SET_NULL, null=True, blank=True, related_name="mentees"
+    )
+
+    class Meta:
+        app_label = "tests"
+
+
+class Tag(models.Model):
+    slug = models.SlugField(primary_key=True, max_length=100)
+    label = models.CharField(max_length=100)
+
+    class Meta:
+        app_label = "tests"
+
+
+class Book(TimestampMixin):
+    title = models.CharField(max_length=300)
+    isbn = models.CharField(max_length=13, unique=True)
+    page_count = models.IntegerField(default=0)
+    is_published = models.BooleanField(default=False)
+    author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name="books")
+    editor = models.ForeignKey(
+        Author,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name="edited_books",
+    )
+    tags = models.ManyToManyField(Tag, blank=True, related_name="books")
+
+    class Meta:
+        app_label = "tests"
+
+
+class Chapter(TimestampMixin):
+    book = models.ForeignKey(Book, on_delete=models.CASCADE, related_name="chapters")
+    number = models.IntegerField()
+    title = models.CharField(max_length=300)
+    word_count = models.IntegerField(default=0)
+
+    class Meta:
+        app_label = "tests"
+        ordering = ["number"]
+        unique_together = [("book", "number")]
+
+
+class Section(models.Model):
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    chapter = models.ForeignKey(
+        Chapter, on_delete=models.CASCADE, related_name="sections"
+    )
+    heading = models.CharField(max_length=300)
+    body = models.TextField(default="")
+    position = models.IntegerField(default=0)
+
+    class Meta:
+        app_label = "tests"
+        ordering = ["position"]
+
+
+class Category(models.Model):
+    name = models.CharField(max_length=200)
+    parent = models.ForeignKey(
+        "self", on_delete=models.CASCADE, null=True, blank=True, related_name="children"
+    )
+
+    class Meta:
+        app_label = "tests"