Extract server route payload handlers

docs/prompt-architecture-improvement-plan.md

@@ -416,13 +416,17 @@ Already isolated:
   by `__init__.py`.
 - generation profile, advanced filter, and ethnicity list utility nodes live in
   `node_profile_filter.py`, with registration maps imported by `__init__.py`.
+- profile-save and accumulator server payload handling lives in
+  `server_routes.py`; `__init__.py` only wires those pure handlers to ComfyUI
+  JSON responses, and `tools/prompt_smoke.py` covers the handlers without
+  importing ComfyUI.
 
 Improve later:
 
 - split remaining large node classes into files by family;
 - keep node display names, return names, and docs in sync through the audit
   helper;
-- add small endpoint tests for profile/accumulator/index-switch routes.
+- add more endpoint tests when new server routes are introduced.
 
 ## Path-Specific Improvements