A channel's message slots are named from the client, on every backend

The IR called them react-message and django-message, so a FastAPI channel had
to declare a DjangoMessage. They are client-message and server-message now,
and the direction words hold wherever a channel is declared: Params /
ClientMessage / ServerMessage, with mizan-core deriving <Pascal>Params and
friends so no backend names a type itself. Django's ReactChannel and
FastAPI's ReactChannel are both Channel.

mizan-fastapi never registered a channels extension, so build_ir() emitted no
channel at all and every payload type was invisible to codegen. It registers
one now. RegistryExtension is an ABC requiring all(), which is what the IR
reads — an extension that cannot enumerate its registrations no longer exists.

The gate that should have caught the rename could not: tests/afi registered no
channel because mizan-rust had no channel registry to register one in, so a
five-package rename of the wire contract passed byte-parity without a channel
byte crossing it. mizan-rust grows ChannelSlotKind, a CHANNELS slice, a
#[mizan::channel] macro, and KDL emission whose wire_to_pascal matches Python's
split; the AFI fixture now carries a channel with every slot and one with a
single slot, so all three backends prove the contract byte for byte.

MizanChannel held three Option<String> beside three has_*() predicates and
unwrapped them with defaults; it holds an ordered slot vector, so an absent
slot is absent rather than defaulted. The channels target emitted a React
hooks file that a stage1-only consumer could not compile — react emits that
now. The codegen's parity tests byte-compared emitted source against baselines
without ever compiling it: they compile the generated crate and run its tests,
import the generated Python package and call every method, and typecheck each
TypeScript target against a consumer.

Also fixed at source: app_visitor printed its import diagnostic to stdout, the
stream export_mizan_ir writes KDL to, so a failed import silently corrupted the
IR; the apps root was hardcoded to "apps"; _default_literal crashed build_ir on
any non-JSON-serializable field default; Django and mizan-core derived Pascal
names two different ways, disagreeing on every dotted channel name.

ir.py builds a document and renders templates/ir/document.kdl.j2 rather than
appending KDL strings with hand-tracked indentation, and named types resolve to
a fixed point — a model reachable only through a union branch was referenced by
a ref that no type block ever defined.

The rest is the write-gate's own classifiers run over the standing tree:
relative imports, silent swallows, Protocol contracts that should be ABCs,
emitters hand-rendering target source, catch-all arms over closed enums, and
comments narrating the project rather than the code.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

examples/django-react-site/mizan.spec.ts

@@ -1,9 +1,6 @@
 /**
- * mizan E2E Integration Tests
- *
- * Real Chromium → Real React app (generated hooks) → Real Django backend
- *
- * Every test uses the generated mizan API, not raw call() or fetch().
+ * Drives a real Chromium against the harness bundle (generated hooks) talking
+ * to the running Django backend. Each fixture is selected by URL hash.
  */
 
 import { test, expect } from '@playwright/test'
@@ -104,14 +101,14 @@ test.describe('error codes from generated hooks', () => {
         expect(['UNAUTHORIZED', 'FORBIDDEN']).toContain(error!.code)
     })
 
-    test('useNotImplementedFn → NOT_IMPLEMENTED', async ({ page }) => {
+    test('useEchoTransform with an unregistered mode → NOT_IMPLEMENTED', async ({ page }) => {
         await fixture(page, 'not-implemented')
         const error = await getError(page)
         expect(error!.type).toBe('MizanError')
         expect(error!.code).toBe('NOT_IMPLEMENTED')
     })
 
-    test('useBuggyFn → INTERNAL_ERROR', async ({ page }) => {
+    test('useDivide by zero → INTERNAL_ERROR', async ({ page }) => {
         await fixture(page, 'internal-error')
         const error = await getError(page)
         expect(error!.type).toBe('MizanError')
@@ -131,7 +128,6 @@ test.describe('error codes from generated hooks', () => {
 test.describe('generated context hooks', () => {
     test('useCurrentUser returns anonymous data', async ({ page }) => {
         await page.goto(`${BASE}#context-current-user`)
-        // Context loads async, wait for result
         await page.waitForSelector('[data-testid="result"]', { timeout: 10000 })
         const result = await getResult(page)
         expect(result.authenticated).toBe(false)
@@ -139,12 +135,10 @@ test.describe('generated context hooks', () => {
     })
 })
 
-// ─── Form hooks ─── (removed; forms codegen deferred per Blazr scope) ──────
-
 // ─── Channel hooks ──────────────────────────────────────────────────────────
 
 test.describe('generated channel hooks', () => {
-    test.skip('useChatChannel receives echoed message', async ({ page }) => {  // channels deferred per Blazr scope
+    test('useChatChannel receives echoed message', async ({ page }) => {
         await page.goto(`${BASE}#channel-chat`)
         await page.waitForFunction(
             () => {