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>

protocol/mizan-codegen/templates/react/react.tsx.j2

@@ -1,7 +1,5 @@
 'use client'
 
-// AUTO-GENERATED by mizan — do not edit
-
 {% set has_contexts = has_global || !named_contexts.is_empty() -%}
 import {
     {% if has_contexts -%}
@@ -30,11 +28,14 @@ import {
 } from '@mizan/base'
 
 {% if !stage1_imports.is_empty() -%}
-import { {{ stage1_imports|join(", ") }} } from './index'
+import {
+{%- for p in stage1_imports.contexts %} fetch{{ p }}Context, type {{ p }}ContextData, type {{ p }}ContextParams,{% endfor %}
+{%- for p in stage1_imports.calls %} call{{ p }},{% endfor %}
+{%- for t in stage1_imports.context_output_types %} type {{ t }},{% endfor %} } from './index'
 
 {% endif -%}
 {% if has_contexts -%}
-// Internal — runs inside a Provider, registers with the kernel exactly once.
+// Runs inside a Provider, registers with the kernel exactly once.
 function useContextSubscription<T>(
     name: string,
     params: Record<string, any>,
@@ -56,7 +57,7 @@ function useContextSubscription<T>(
 }
 {% endif %}
 
-// Internal — wraps an imperative call() with isPending / error state.
+// Wraps an imperative call() with isPending / error state.
 interface MutationHook<TArgs, TResult> {
     mutate: (args: TArgs) => Promise<TResult>
     isPending: boolean
@@ -85,8 +86,6 @@ function useMutation<TArgs, TResult>(
     return { mutate, isPending, error }
 }
 {% if has_global %}
-// ── Global Context ──
-
 const GlobalCtx = createContext<ContextState<GlobalContextData> | null>(null)
 
 export function GlobalContextProvider({ children }: { children: ReactNode }) {
@@ -107,8 +106,6 @@ export function use{{ fn.pascal }}(): {{ fn.output_type }} | null {
 {% endfor -%}
 {% endif -%}
 {% for ctx in named_contexts %}
-// ── {{ ctx.pascal }} Context ──
-
 const {{ ctx.pascal }}Ctx = createContext<ContextState<{{ ctx.pascal }}ContextData> | null>(null)
 
 {% if ctx.has_params -%}
@@ -144,8 +141,6 @@ export function use{{ call.pascal }}() {
 }
 {% endif -%}
 {% endfor %}
-// ── MizanContext root provider ──
-
 export interface MizanContextProps {
     /** Base URL for protocol endpoints. Defaults to "/api/mizan". */
     baseUrl?: string
@@ -155,8 +150,8 @@ export interface MizanContextProps {
 }
 
 /**
- * Root provider — calls configure() once and mounts the global context (if defined).
- * Must wrap any component using Mizan-generated hooks.
+ * Calls configure() once and mounts the global context when one is defined.
+ * Every component reading a generated hook resolves through this provider.
  */
 export function MizanContext({ baseUrl, session, children }: MizanContextProps) {
     const configured = useRef(false)
@@ -174,12 +169,7 @@ export function MizanContext({ baseUrl, session, children }: MizanContextProps)
 {%- endif %}
 }
 
-// ── Imperative escape hatch ──
-
-/**
- * Returns the imperative kernel API. For test harnesses or rare cases where
- * a typed generated hook does not fit. Most app code should use the typed hooks.
- */
+/** The untyped kernel entry points, bound to the configured client. */
 export function useMizan() {
     return { call: mizanCall, fetch: mizanFetch }
 }