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/vue/vue.ts

@@ -0,0 +1,96 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { ref, computed, onMounted, onUnmounted, onServerPrefetch, type ComputedRef } from 'vue'
+import { registerContext, type ContextState } from '@mizan/base'
+
+import { fetchUserContext, type UserContextData, type UserContextParams, callUpdateProfile, callEcho, callWhoami, callFindUser, callRenameUser } from '../index'
+
+export function useUserContext(params: UserContextParams) {
+    const state = ref<ContextState<UserContextData>>({ data: null, status: 'idle', error: null })
+    let handle: ReturnType<typeof registerContext> | null = null
+
+    onMounted(() => {
+        handle = registerContext('user', params, () => fetchUserContext(params))
+        handle.subscribe(() => { state.value = handle!.getState() })
+        handle.refetch()
+    })
+
+    onServerPrefetch(async () => {
+        handle = registerContext('user', params, () => fetchUserContext(params))
+        await handle.refetch()
+        state.value = handle.getState()
+    })
+
+    onUnmounted(() => { handle?.unregister() })
+
+    return {
+        state,
+        userProfile: computed(() => state.value.data?.user_profile ?? null) as ComputedRef<userProfileOutput | null>,
+        userOrders: computed(() => state.value.data?.user_orders ?? null) as ComputedRef<userOrdersOutput | null>,
+        loading: computed(() => state.value.status === 'loading'),
+        error: computed(() => state.value.error),
+    }
+}
+
+export function useUpdateProfile() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate(args: Parameters<typeof callUpdateProfile>[0]) {
+        isPending.value = true; error.value = null
+        try { return await callUpdateProfile(args) }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export function useEcho() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate(args: Parameters<typeof callEcho>[0]) {
+        isPending.value = true; error.value = null
+        try { return await callEcho(args) }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export function useWhoami() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate() {
+        isPending.value = true; error.value = null
+        try { return await callWhoami() }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export function useFindUser() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate(args: Parameters<typeof callFindUser>[0]) {
+        isPending.value = true; error.value = null
+        try { return await callFindUser(args) }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export function useRenameUser() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate(args: Parameters<typeof callRenameUser>[0]) {
+        isPending.value = true; error.value = null
+        try { return await callRenameUser(args) }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export type { ContextState } from '@mizan/base'
+export { configure, initSession, MizanError } from '@mizan/base'