feat(ipython): add data helpers without persisted history (#510)

Add a dedicated IPython module with startup helpers for JSON, YAML, TOML, and CSV plus a small set of common standard-library imports for interactive use.

Disable SQLite history and stop preserving ~/.ipython: interactive sessions can contain credentials and other sensitive data, so that profile state must not survive reboots implicitly.

Assisted-by: DeepSeek Harness 0.2.2-alpha.2 (deepseek-flash)

hosts/idols-ai/preservation.nix

@@ -216,7 +216,10 @@ in
         ".config/Joplin" # joplin-desktop
 
         ".local/share/jupyter"
-        ".ipython"
+        # Deliberately not persisted: ~/.ipython contains history.sqlite, and
+        # interactive sessions may contain credentials or other sensitive
+        # values. Home Manager recreates the profile config and startup helpers
+        # from the Nix store on every activation.
 
         # ======================================
         # Cloud Native