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>

frontends/mizan-react/src/channels/index.ts

@@ -1,64 +1,9 @@
-/**
- * mizan/channels
- *
- * Real-time WebSocket communication with Django Channels.
- * Type-safe bidirectional messaging.
- *
- * ## Setup
- *
- * ```tsx
- * // layout.tsx
- * import { ChannelProvider } from 'mizan/channels'
- *
- * export default function Layout({ children }) {
- *     return (
- *         <ChannelProvider>
- *             {children}
- *         </ChannelProvider>
- *     )
- * }
- * ```
- *
- * ## Usage
- *
- * ```tsx
- * // Using generated hooks (recommended)
- * import { useChatChannel } from '@/api/generated.channels'
- *
- * function Chat({ room }) {
- *     const chat = useChatChannel({ room })
- *
- *     chat.status     // 'connecting' | 'connected' | 'disconnected'
- *     chat.messages   // DjangoMessage[]
- *     chat.send({ text: 'Hello' })  // Send ReactMessage
- * }
- * ```
- *
- * ```tsx
- * // Using raw hook (for custom channels)
- * import { useChannel } from 'mizan/channels'
- *
- * function CustomChannel() {
- *     const channel = useChannel<
- *         { room: string },           // Params
- *         { user: string; text: string },  // DjangoMessage
- *         { text: string }            // ReactMessage
- *     >('chat', { room: 'general' })
- *
- *     // ...
- * }
- * ```
- */
-
-// Context
 export { ChannelProvider, useChannelContext, useChannelStatus } from './context'
 export type { ChannelProviderProps } from './context'
 
-// Hooks
 export { useChannel, useChannelLatest, useRPC, RPCError } from './hooks'
 export type { UseChannelOptions, RPCClient } from './hooks'
 
-// Connection (for advanced use)
 export { ChannelConnection, getDefaultConnection } from './connection'
 export type {
     ChannelConnectionOptions,
@@ -68,7 +13,6 @@ export type {
     RPCErrorResponse,
 } from './connection'
 
-// Types
 export type {
     ConnectionStatus,
     ChannelSubscription,