Restore KDL-as-IR to AFI_ARCHITECTURE

Re-stating the architectural intent that got silently swapped to "JSON
schema" during the doc-restoration commit (6eca514). The original
AFI_ARCHITECTURE positioned KDL as the LLVM-IR-equivalent of the
system; I read the stale-package-name note at the bottom as
invalidating the whole architecture description and substituted
JSON-schema references thinking that was the more-current intent.

That conflated implementation drift (mizan-ast/mizan-schema package
names) with substrate intent (KDL is the IR). The packages had
drifted; the IR target had not. Restoring the section.

Frames KDL-as-IR explicitly as forward-direction. The current
OpenAPI/JSON-Schema codegen path is transitional — it's the layered
indirection where adapter divergence lives (AFI conformance suite
demonstrates this). Real KDL implementation lives in a forthcoming
mizan-schema package; today's path is sediment around the eventual
substrate.

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

docs/AFI_ARCHITECTURE.md

@@ -38,12 +38,34 @@ against the raw kernel — so a React developer gets `useEcho()` and
 `<MizanContext>`, a Vue developer gets `useEcho()` composables, a
 Svelte developer gets readable stores. Same kernel underneath.
 
-## Schema is load-bearing
+## KDL is the IR
 
-The backend exports a JSON schema describing every `@client`-decorated
+The Mizan IR is **KDL** — the LLVM-IR-equivalent of the system. Every
-function and context (`x-mizan-functions`, `x-mizan-contexts`). The
+backend adapter produces KDL describing its registered functions,
-schema IS the contract: codegen reads it, the edge manifest derives
+contexts, types, and invalidation graph. Every codegen target consumes
-from it, MWT auth gates against it.
+KDL. KDL is the contract; everything else (REST envelopes, OpenAPI
+documents, framework idioms) is sediment around it.
+
+The IR must be validated against multiple adapters before it is
+considered stable. Single-adapter validation hides assumptions —
+divergence between adapters is what the IR exists to prevent.
+
+Forward-direction primitives:
+
+- `cores/mizan-python` builds the IR from registered functions
+  (`build_ir()` walks `mizan_core.registry`, emits KDL)
+- A `mizan-schema` package (forthcoming) holds the canonical KDL
+  grammar / type system definition that every adapter targets
+- Codegen reads KDL directly — no OpenAPI envelope, no
+  `openapi-typescript`, no per-backend converter divergence
+- Edge manifest, MWT claims, and other protocol artifacts all derive
+  from the same KDL
+
+**Current implementation is transitional.** Today the codegen consumes
+OpenAPI 3.0 (`x-mizan-functions` + `x-mizan-contexts` extensions over
+Pydantic→JSON-Schema), produced via Django Ninja or FastAPI's native
+generator. That layered indirection is what introduces adapter
+divergence (see the AFI conformance suite). KDL-as-IR collapses it.
 
 ## Launch surface