Mizan IR: cut over to KDL, delete OpenAPI envelope

Replaces the transitional OpenAPI 3.0 + `x-mizan-*` extensions
substrate with the canonical Mizan IR as KDL, per docs/AFI_ARCHITECTURE.md:
"KDL is the contract; everything else (REST envelopes, OpenAPI
documents, framework idioms) is sediment around it."

End-to-end cutover. No transitional path left on main.

Forward direction:
  cores/mizan-python/src/mizan_core/ir.py
    build_ir() walks mizan_core.registry, introspects Pydantic
    models directly (no JSON-Schema indirection), and emits the
    Mizan IR document. The KDL grammar is locked in this file's
    module docstring.

Backends emit KDL:
  backends/mizan-fastapi/src/mizan_fastapi/ir.py
    `python -m mizan_fastapi.ir <module>` — CLI entry point.
  backends/mizan-django/.../management/commands/export_mizan_ir.py
    `manage.py export_mizan_ir` — Django mgmt command.

Codegen consumes KDL:
  protocol/mizan-codegen/Cargo.toml: + kdl = "6"
  protocol/mizan-codegen/src/ir.rs: NamedType { Struct/List/Enum/Alias }
    + TypeShape { Primitive/Ref/List/Optional/Enum/Union } sum types,
    replacing the JsonSchema sprawl. KDL parser walks the
    `kdl::KdlDocument` tree into typed Rust structs.
  protocol/mizan-codegen/src/fetch.rs: subprocess command switches
    to the new IR-export entry points.
  All emit modules (stage1 / react / python / rust / vue / svelte /
    channels) port their type-walkers from JsonSchema to the new
    sum types — case analysis collapses substantially.

Substrate-honesty wins beyond the moat closure:
  - `int | bool` multi-arm unions land as `TypeShape::Union` (was
    silently coerced to "string" before).
  - `<CamelName>Output = list[T]` returns emit as named alias
    types instead of struct-shaped wrappers, so consumer code
    `.map()` works directly on the type.
  - Pydantic field defaults flow through to `default` properties
    in KDL, then back to non-optional shape in every target.

Deleted:
  - backends/mizan-fastapi/src/mizan_fastapi/{cli,schema}.py
  - backends/mizan-django/.../export_mizan_schema.py
  - openapi-bearing half of mizan/export/__init__.py (edge
    manifest generator preserved — separate concern).
  - tests/afi/schema_normalizer.py
  - tests/fixtures/{afi_schema.json, channels_schema.json}
  - tests/fixtures/js_* baseline directories.

Verification:
  - 20 mizan-codegen unit tests green (IR deserialization,
    byte-equivalence parity across stage1/rust/python/react/vue/svelte
    against fresh KDL-driven baselines, channels structural).
  - tests/rust/run_wire_parity.py: 12/12 probes green driving
    the binary end-to-end through KDL.
  - Blazr studio-ui typechecks against the regenerated React client.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

protocol/mizan-codegen/tests/fixtures/baselines/svelte/contexts/user.ts

@@ -0,0 +1,18 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanFetch } from '@mizan/base'
+
+import type { userProfileOutput, userOrdersOutput } from '../types'
+
+export interface UserContextData {
+    user_profile: userProfileOutput
+    user_orders: userOrdersOutput
+}
+
+export interface UserContextParams {
+    user_id: number
+}
+
+export function fetchUserContext(params: UserContextParams): Promise<UserContextData> {
+    return mizanFetch('user', params)
+}

protocol/mizan-codegen/tests/fixtures/baselines/svelte/functions/echo.ts

@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { echoInput, echoOutput } from '../types'
+
+export function callEcho(args: echoInput): Promise<echoOutput> {
+    return mizanCall('echo', args)
+}

protocol/mizan-codegen/tests/fixtures/baselines/svelte/functions/findUser.ts

@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { findUserInput, findUserOutput } from '../types'
+
+export function callFindUser(args: findUserInput): Promise<findUserOutput> {
+    return mizanCall('find_user', args)
+}

protocol/mizan-codegen/tests/fixtures/baselines/svelte/functions/renameUser.ts

@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { renameUserInput, renameUserOutput } from '../types'
+
+export function callRenameUser(args: renameUserInput): Promise<renameUserOutput> {
+    return mizanCall('rename_user', args)
+}

protocol/mizan-codegen/tests/fixtures/baselines/svelte/functions/whoami.ts

@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { whoamiOutput } from '../types'
+
+export function callWhoami(): Promise<whoamiOutput> {
+    return mizanCall('whoami', {})
+}

protocol/mizan-codegen/tests/fixtures/baselines/svelte/index.ts

@@ -0,0 +1,14 @@
+// AUTO-GENERATED by mizan — do not edit
+
+export * from './types'
+
+export { fetchUserContext, type UserContextData, type UserContextParams } from './contexts/user'
+
+export { callEcho } from './functions/echo'
+export { callWhoami } from './functions/whoami'
+export { callUpdateProfile } from './mutations/updateProfile'
+export { callFindUser } from './functions/findUser'
+export { callRenameUser } from './functions/renameUser'
+
+// Stage 2 framework adapter
+export * from './svelte'

protocol/mizan-codegen/tests/fixtures/baselines/svelte/mutations/updateProfile.ts

@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { updateProfileInput, updateProfileOutput } from '../types'
+
+export function callUpdateProfile(args: updateProfileInput): Promise<updateProfileOutput> {
+    return mizanCall('update_profile', args)
+}

protocol/mizan-codegen/tests/fixtures/baselines/svelte/svelte.ts

@@ -0,0 +1,29 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { readable, type Readable } from 'svelte/store'
+import { registerContext, type ContextState } from '@mizan/base'
+
+import { fetchUserContext, type UserContextData, type UserContextParams, callUpdateProfile, callEcho, callWhoami, callFindUser, callRenameUser } from '../index'
+
+export function createUserContext(params: UserContextParams) {
+    const store = readable<ContextState<UserContextData>>(
+        { data: null, status: 'idle', error: null },
+        (set) => {
+            const handle = registerContext('user', params, () => fetchUserContext(params))
+            const unsub = handle.subscribe(() => set(handle.getState()))
+            handle.refetch()
+            return () => { unsub(); handle.unregister() }
+        },
+    )
+
+    return store
+}
+
+export { callUpdateProfile } from '../index'
+export { callEcho } from '../index'
+export { callWhoami } from '../index'
+export { callFindUser } from '../index'
+export { callRenameUser } from '../index'
+
+export type { ContextState } from '@mizan/base'
+export { configure, initSession, MizanError } from '@mizan/base'

protocol/mizan-codegen/tests/fixtures/baselines/svelte/types.ts

@@ -0,0 +1,64 @@
+// AUTO-GENERATED by mizan — do not edit
+
+export interface OrderOutput {
+    id: number
+    user_id: number
+    total: number
+}
+
+export interface echoInput {
+    text: string
+}
+
+export interface echoOutput {
+    message: string
+}
+
+export interface findUserInput {
+    user_id: number
+}
+
+export interface findUserOutput {
+    user_id: number
+    name: string
+}
+
+export interface renameUserInput {
+    user_id: number
+    name: string
+}
+
+export interface renameUserOutput {
+    user_id: number
+    name: string
+}
+
+export interface updateProfileInput {
+    user_id: number
+    name: string
+}
+
+export interface updateProfileOutput {
+    ok: boolean
+}
+
+export interface userOrdersInput {
+    user_id: number
+}
+
+export type userOrdersOutput = OrderOutput[]
+
+export interface userProfileInput {
+    user_id: number
+}
+
+export interface userProfileOutput {
+    user_id: number
+    name: string
+}
+
+export interface whoamiOutput {
+    email: string
+    authenticated: boolean
+}
+