Land CSOC-WP-0006 PageOps: member space/page CRUD, copy, transfer

Thin CONTENT_ROOT content plane (ADR-0003/0004) with space visual field,
product UI for Title/Abstract/Visual, page list sidebar, and tests. Update
capability model and smoke checklist; mark WP-0006 finished.

coulomb_social/settings/test.py

@@ -1,3 +1,5 @@
+from pathlib import Path
+
 from .base import *  # noqa: F403
 
 DEBUG = False
@@ -15,6 +17,9 @@ OIDC_ENABLED = False
 USER_ENGINE_BASE_URL = ""
 FLEX_AUTH_BASE_URL = ""
 
+# Isolate content plane from developer var/ trees during tests
+CONTENT_ROOT = str(Path(BASE_DIR) / "var" / "test-content")  # noqa: F405
+
 # Whitenoise manifest not required in tests
 STORAGES = {
     "staticfiles": {