Fix remaining cache issues: index TTL, sub-index cleanup, top-level imports

- RedisCache.put: add pipe.expire() on index sets matching entry TTL,
  prevents orphaned index entries when cache values expire
- Broad purge: delete_indexes_by_prefix() cleans per-param sub-indexes
  (mizan:idx:ctx:k=v) that previously leaked as dead sets
- Move cache imports to top of executor.py (were inline in view functions)
- Update KNOWN_ISSUES.md — all 16 issues now resolved or documented

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/mizan-django/src/mizan/cache/__init__.py

@@ -172,6 +172,9 @@ def cache_purge(
         keys_to_delete = backend.get_index(index_key)
         backend.delete_index(index_key)
 
+        # Clean up per-param sub-indexes (e.g., mizan:idx:user:user_id=5)
+        backend.delete_indexes_by_prefix(f"mizan:idx:{context}:")
+
         if keys_to_delete:
             return backend.delete_many(list(keys_to_delete))
         return 0

packages/mizan-django/src/mizan/cache/backend.py

@@ -20,6 +20,7 @@ class CacheBackend(Protocol):
     def get_index(self, index_key: str) -> set[str]: ...
     def remove_from_index(self, index_key: str, members: set[str]) -> None: ...
     def delete_index(self, index_key: str) -> None: ...
+    def delete_indexes_by_prefix(self, prefix: str) -> None: ...
     def clear(self) -> None: ...
 
 
@@ -65,6 +66,11 @@ class MemoryCache:
     def delete_index(self, index_key: str) -> None:
         self._indexes.pop(index_key, None)
 
+    def delete_indexes_by_prefix(self, prefix: str) -> None:
+        to_delete = [k for k in self._indexes if k.startswith(prefix)]
+        for k in to_delete:
+            del self._indexes[k]
+
     def clear(self) -> None:
         self._store.clear()
         self._indexes.clear()
@@ -116,6 +122,7 @@ class RedisCache:
         pipe.set(prefixed_key, value, ex=self._ttl)
         for idx in indexes:
             pipe.sadd(self._key(idx), key)
+            pipe.expire(self._key(idx), self._ttl)
         pipe.execute()
 
     def delete_many(self, keys: list[str]) -> int:
@@ -135,6 +142,19 @@ class RedisCache:
     def delete_index(self, index_key: str) -> None:
         self._client.delete(self._key(index_key))
 
+    def delete_indexes_by_prefix(self, prefix: str) -> None:
+        pattern = f"{self._prefix}{prefix}*"
+        cursor = 0
+        while True:
+            cursor, keys = self._client.scan(cursor, match=pattern, count=100)
+            if keys:
+                pipe = self._client.pipeline()
+                for key in keys:
+                    pipe.unlink(key)
+                pipe.execute()
+            if cursor == 0:
+                break
+
     def clear(self) -> None:
         pattern = f"{self._prefix}*"
         cursor = 0

packages/mizan-django/src/mizan/client/executor.py

@@ -27,7 +27,9 @@ from django.http import HttpRequest, HttpResponse, JsonResponse
 from django.views.decorators.csrf import csrf_protect
 from pydantic import BaseModel, ValidationError
 
+from mizan.cache import get_cache, cache_get, cache_put, cache_purge
 from mizan.setup.registry import get_function, get_context_groups
+from mizan.setup.settings import get_settings
 
 if TYPE_CHECKING:
     pass
@@ -662,8 +664,6 @@ def function_call_view(request: HttpRequest) -> JsonResponse:
         response["X-Mizan-Invalidate"] = _format_invalidate_header(invalidate_contexts)
 
         # Purge origin-side cache for invalidated contexts
-        import logging
-        from mizan.cache import get_cache, cache_purge
         _cache_log = logging.getLogger("mizan.cache")
         cache = get_cache()
         if cache is not None:
@@ -776,9 +776,6 @@ def context_fetch_view(request: HttpRequest, context_name: str) -> JsonResponse:
     params = request.GET.dict()
 
     # Origin-side cache lookup
-    import logging
-    from mizan.cache import get_cache, cache_get, cache_put
-    from mizan.setup.settings import get_settings
     _cache_log = logging.getLogger("mizan.cache")
     cache = get_cache()
     cache_settings = get_settings()