Restore documentation layer — match current substrate

ROADMAP: done items moved out of "Next" (codegen rewrite, SSR bridge,
edge manifest, X-Mizan-Invalidate, return-type branching, affects_params,
kernel extraction, two-stage codegen, mizan-ts). Real "Next" in:
framework-adapter wrapper layer (MizanContext + useMizan + DjangoError
on top of the kernel) for React/Vue/Svelte; A1–A4 from ISSUES.md.

CLAUDE: 4-package layout replaced with the actual 7-package layered
architecture (backend protocol adapters + frontend kernel + framework
adapters + SSR worker). "STALE codegen" section rewritten to describe
what's emitted vs. the wrapper layer that isn't yet.

docs/ now tracked (6 files). AFI_ARCHITECTURE rewritten — replaced
the speculative `mizan-ast`/`mizan-csr`/`mizan-rpc`/`mizan-schema`
package names with the real layout, dropped KDL-schema language for
the actual schema-export format. The other 5 docs/ files were already
current and are tracked as-is.

ARCHITECTURE-REWORK.md deleted — same expert review is re-tracked in
the fresher ISSUES.md, two parallel trackers was sediment.

README.md deleted — drift was beyond surgical fixes (`mizan_clients.py`
convention, `<DjangoContext>` provider, removed `@compose` and
`context='local'`, wrong codegen output filenames, 3-package structure
vs. 7). Rewrite waits for the wrapper-layer codegen to land so
user-facing examples reflect reality.

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

docs/SSR_ARCHITECTURE.md

@@ -0,0 +1,50 @@
+# SSR Architecture
+
+*Decided 2026-04-07.*
+
+Mizan's SSR adapter is a **Django template backend**. It plugs into
+Django's existing `TEMPLATES` setting, replacing the template
+rendering engine.
+
+```python
+TEMPLATES = [
+    {
+        'BACKEND': 'mizan.ssr.MizanTemplates',
+        ...
+    }
+]
+```
+
+Then `render(request, 'ProfilePage', context)` calls the Bun
+subprocess bridge instead of rendering a Django/Jinja2 template.
+**The component name IS the template name.**
+
+## AFI boundary
+
+| Side | Responsibility |
+|---|---|
+| Backend adapter | Implements `mizan.ssr()` — executes context functions, gathers data |
+| Frontend adapter | Implements `renderToHTML()` — takes component + props, produces HTML |
+| Bun subprocess | Hosts the frontend adapter |
+| stdin/stdout JSON-RPC | Transport between the two |
+
+## Why template backend
+
+- Django's template system is swappable by design (batteries
+  included, but replaceable).
+- Django developers already use `render(request, template, context)`
+  — no new API to learn.
+- URL routing, views, middleware, auth — all unchanged.
+- The template tag `{% mizan_render %}` is a convenience for
+  developers who *also* use Django templates (e.g., a base.html shell
+  with Mizan components inside).
+
+## Implementation surface
+
+The SSR bridge module implements Django's template backend interface:
+
+- `BaseEngine` subclass
+- `Template` class with `.render(context, request)`
+
+Everything Django expects from a template backend, but the actual
+rendering routes to Bun.