Restructure tree by role; rename mizan-runtime → mizan-base

packages/ flattens into:
  backends/   server protocol adapters (mizan-django, mizan-ts)
  frontends/  client kernel + framework adapters (mizan-base, mizan-react, mizan-vue, mizan-svelte)
  workers/    runtime workers (mizan-ssr)
  cores/      shared language-level primitives (empty for now; mizan-python forthcoming)

The frontend kernel (was packages/mizan-runtime, now frontends/mizan-base) is
renamed to reflect its role — it's the shared base that frontend adapters
depend on directly. Reflects the substrate position that per-framework adapters
wrap a single shared kernel; codegen targets the adapter, not the raw kernel.

Path updates landed in: Makefile, two Gitea workflows, Dockerfile.test, four
example/harness config files, .claude/settings.local.json, four docs
(CLAUDE/ISSUES/ROADMAP/AFI_ARCHITECTURE), four codegen templates (stage1 +
react/vue/svelte adapters), and three package.jsons (the mizan-base rename
plus mizan-vue/svelte peerDeps).

Generated files under examples/django-react-site/harness/src/api/ still
reference @mizan/runtime — left as-is; they're regenerated artifacts and
the harness is non-functional pending the React wrapper-layer codegen.

Also folded in a pre-existing fix: the Gitea workflows had
working-directory: react / django pointing at a layout that predates
packages/, never updated.

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

backends/mizan-ts/src/cache/backend.ts

@@ -0,0 +1,44 @@
+/**
+ * Cache backends — MemoryCache for testing.
+ *
+ * Simple key-value store. No reverse indexes.
+ */
+
+export interface CacheBackend {
+    get(key: string): string | null
+    set(key: string, value: string): void
+    delete(key: string): boolean
+    deleteByPrefix(prefix: string): number
+    clear(): void
+}
+
+export class MemoryCache implements CacheBackend {
+    private _store = new Map<string, string>()
+
+    get(key: string): string | null {
+        return this._store.get(key) ?? null
+    }
+
+    set(key: string, value: string): void {
+        this._store.set(key, value)
+    }
+
+    delete(key: string): boolean {
+        return this._store.delete(key)
+    }
+
+    deleteByPrefix(prefix: string): number {
+        let count = 0
+        for (const key of [...this._store.keys()]) {
+            if (key.startsWith(prefix)) {
+                this._store.delete(key)
+                count++
+            }
+        }
+        return count
+    }
+
+    clear(): void {
+        this._store.clear()
+    }
+}