Mizan-Rust backend adapter: server-side substrate + three-way parity

Adds first-class Rust-backed Mizan to sit alongside mizan-django and
mizan-fastapi. A Rust dev writes:

    #[derive(Mizan, Serialize, Deserialize)]
    pub struct ProfileOutput { pub user_id: i64, pub name: String }

    #[mizan::context("user")]
    pub struct UserCtx;

    #[mizan::client(context = UserCtx)]
    pub async fn user_profile(_req: &RequestHandle<'_>, user_id: i64) -> ProfileOutput { ... }

…and gets byte-identical KDL to the Python emitters, served over the
same wire protocol the React / Rust / Vue / Svelte kernels speak.

New crates:
- cores/mizan-rust/         (Cargo: mizan-core)     — IR types, KDL emitter, traits, registry,
                                                       runtime (compute_invalidation / compute_merges
                                                       ported from mizan-fastapi), graph_check with
                                                       structural type-matching
- cores/mizan-rust-macros/  (Cargo: mizan-macros)   — #[derive(Mizan)], #[mizan::context],
                                                       #[mizan::client] proc macros
- backends/mizan-rust-axum/ (Cargo: mizan-axum)     — axum HTTP adapter: /session/, /call/, /ctx/:name/
- tests/afi/rust_app/                                — AFI fixture port + server / export-ir binaries

Substrate-shape moves required by cross-language equivalence:
- IR canonicalization: functions / contexts / context-members / shared-by
  now sort alphabetically in both Python and Rust emitters. The IR is a
  contract; linkme doesn't preserve declaration order, so canonical sort
  is the only stable mapping. afi_ir.kdl + per-target baselines regenerated.
- MizanType::TYPE_NAME is a const (with a default type_name() reader) so
  it's usable in linkme TypeEntry static initializers.
- Tree-shaken type registry: #[derive(Mizan)] only emits the trait impl;
  the #[mizan::client] macro registers canonical-named entries from
  fn signatures, including Vec<T> element types for ref resolution.
- Merge resolution is structural (NamedType shape comparison) rather than
  by name — matches the Python types_match_for_merge semantics.

Three-way forcing functions:
- tests/afi/test_codegen_parity.py — Django ≡ FastAPI ≡ Rust on KDL bytes (3 pass)
- tests/rust/run_wire_parity.py    — 12/12 probes against FastAPI + Rust (EXIT=0)

Incidental fixes surfaced by the new tests:
- Stale `from .registry import validate_registry` import removed from
  mizan-django/setup/discovery.py (referenced a function that no longer
  exists; was masking codegen-parity).
- BASE_DIR added to tests/afi/django_app/project/settings.py.
- /session/ endpoint added to mizan-fastapi for protocol-shaped readiness
  probe parity (wire-parity harness now polls /api/mizan/session/ on both
  backends rather than FastAPI's /openapi.json).
- Root .gitignore picks up Rust target/ across the tree so new crates
  don't need per-crate gitignore.

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

protocol/mizan-codegen/tests/fixtures/baselines/react/react.tsx

@@ -22,7 +22,7 @@ import {
     type ContextState,
 } from '@mizan/base'
 
-import { fetchUserContext, type UserContextData, type UserContextParams, callUpdateProfile, callEcho, callWhoami, callFindUser, callRenameUser, type userProfileOutput, type userOrdersOutput } from './index'
+import { fetchUserContext, type UserContextData, type UserContextParams, callUpdateProfile, callEcho, callFindUser, callRenameUser, callWhoami, type userOrdersOutput, type userProfileOutput } from './index'
 
 // Internal — runs inside a Provider, registers with the kernel exactly once.
 function useContextSubscription<T>(
@@ -89,14 +89,14 @@ export function useUserContext(): ContextState<UserContextData> {
     return ctx
 }
 
-export function useUserProfile(): userProfileOutput | null {
-    return useUserContext().data?.user_profile ?? null
-}
-
 export function useUserOrders(): userOrdersOutput | null {
     return useUserContext().data?.user_orders ?? null
 }
 
+export function useUserProfile(): userProfileOutput | null {
+    return useUserContext().data?.user_profile ?? null
+}
+
 export function useUpdateProfile() {
     return useMutation<Parameters<typeof callUpdateProfile>[0], Awaited<ReturnType<typeof callUpdateProfile>>>(callUpdateProfile)
 }
@@ -105,10 +105,6 @@ export function useEcho() {
     return useMutation<Parameters<typeof callEcho>[0], Awaited<ReturnType<typeof callEcho>>>(callEcho)
 }
 
-export function useWhoami() {
-    return useMutation<void, Awaited<ReturnType<typeof callWhoami>>>(() => callWhoami() as any)
-}
-
 export function useFindUser() {
     return useMutation<Parameters<typeof callFindUser>[0], Awaited<ReturnType<typeof callFindUser>>>(callFindUser)
 }
@@ -117,6 +113,10 @@ export function useRenameUser() {
     return useMutation<Parameters<typeof callRenameUser>[0], Awaited<ReturnType<typeof callRenameUser>>>(callRenameUser)
 }
 
+export function useWhoami() {
+    return useMutation<void, Awaited<ReturnType<typeof callWhoami>>>(() => callWhoami() as any)
+}
+
 // ── MizanContext root provider ──
 
 export interface MizanContextProps {