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)

home/base/tui/editors/README.md

@@ -7,5 +7,5 @@ closure.
 Editor programs, keymaps, `$EDITOR` defaults, and usage docs live under
 [`../../core/editors/`](../../core/editors/README.md) (Helix, Neovim backup, glossary, cheatsheets).
 
-[`default.nix`](./default.nix) imports `./packages.nix` so `home/base/tui` can keep pulling in
-tooling without mixing it into `core/editors`.
+[`default.nix`](./default.nix) imports [`ipython/`](./ipython/) and `./packages.nix` so
+`home/base/tui` can keep pulling in tooling without mixing it into `core/editors`.

home/base/tui/editors/default.nix

@@ -1,4 +1,7 @@
 # Editor-related language servers and heavy tooling — kept out of `core/editors`.
 {
-  imports = [ ./packages.nix ];
+  imports = [
+    ./ipython
+    ./packages.nix
+  ];
 }

home/base/tui/editors/ipython/README.md

@@ -0,0 +1,13 @@
+# IPython
+
+[`default.nix`](./default.nix) manages `~/.ipython/profile_default` with two pieces:
+
+- `ipython_config.py` disables SQLite history because interactive sessions may contain secrets.
+- `startup/10-data-helpers.py` loads JSON, YAML, TOML, and CSV helpers at every IPython start. It
+  also pre-imports a small set of common standard-library names such as `Path`, `Counter`, and
+  `datetime`.
+
+[`data-helpers.py`](./data-helpers.py) deliberately keeps heavier libraries such as NumPy and pandas
+out of startup; import them explicitly when needed. The `~/.ipython` profile is not persisted by
+`hosts/idols-ai/preservation.nix`, so Home Manager recreates the config and helpers from the Nix
+store on every activation.

home/base/tui/editors/ipython/data-helpers.py

@@ -0,0 +1,102 @@
+# ruff: noqa: F401
+"""IPython startup helpers for inspecting structured data.
+
+IPython executes files in this profile's startup directory before the first
+prompt, so these helpers are available in every interactive session.
+"""
+
+# A small set of common names preloaded for interactive use. The unused-import
+# exception is intentional: IPython exposes these names directly in the prompt.
+import csv
+import io
+import json
+import os
+import re
+import shutil
+import subprocess
+import sys
+import tomllib
+from collections import Counter, defaultdict
+from datetime import date, datetime, timedelta, timezone
+from pathlib import Path
+from pprint import pprint
+
+import toml
+import yaml
+
+
+def loads_json(text: str):
+    return json.loads(text)
+
+
+def dumps_json(value, indent: int = 2) -> str:
+    return json.dumps(value, ensure_ascii=False, indent=indent)
+
+
+def loads_yaml(text: str):
+    return yaml.safe_load(text)
+
+
+def dumps_yaml(value) -> str:
+    return yaml.safe_dump(value, allow_unicode=True, sort_keys=False)
+
+
+def loads_toml(text: str):
+    return tomllib.loads(text)
+
+
+def dumps_toml(value) -> str:
+    return toml.dumps(value)
+
+
+def loads_csv(text: str) -> list[dict[str, str]]:
+    return list(csv.DictReader(io.StringIO(text)))
+
+
+def dumps_csv(rows, fieldnames=None) -> str:
+    rows = list(rows)
+    if not rows:
+        return ""
+
+    fieldnames = fieldnames or list(rows[0])
+    buffer = io.StringIO(newline="")
+    writer = csv.DictWriter(buffer, fieldnames=fieldnames)
+    writer.writeheader()
+    writer.writerows(rows)
+    return buffer.getvalue()
+
+
+def show(value):
+    """Pretty-print a value and return it for further use."""
+    pprint(value, width=120, sort_dicts=False)
+    return value
+
+
+def show_json(text: str):
+    return show(loads_json(text))
+
+
+def show_yaml(text: str):
+    return show(loads_yaml(text))
+
+
+def show_toml(text: str):
+    return show(loads_toml(text))
+
+
+def show_csv(text: str):
+    return show(loads_csv(text))
+
+
+def copy_to_clipboard(text: str) -> str:
+    """Copy text to the system clipboard and return it."""
+    commands = (
+        [["pbcopy"]]
+        if sys.platform == "darwin"
+        else [["wl-copy"], ["xclip", "-selection", "clipboard"]]
+    )
+    for command in commands:
+        if shutil.which(command[0]):
+            subprocess.run(command, input=text, text=True, check=True)
+            return text
+    raise RuntimeError("No clipboard command found (need wl-copy, xclip, or pbcopy)")

home/base/tui/editors/ipython/default.nix

@@ -0,0 +1,14 @@
+{ ... }:
+{
+  # Interactive IPython sessions routinely handle credentials and other
+  # sensitive values, so keep the SQLite history disabled rather than relying
+  # on the profile directory's lifetime. Home Manager recreates these files
+  # from the Nix store on every activation.
+  home.file = {
+    ".ipython/profile_default/ipython_config.py".text = ''
+      c = get_config()
+      c.HistoryManager.enabled = False
+    '';
+    ".ipython/profile_default/startup/10-data-helpers.py".source = ./data-helpers.py;
+  };
+}

home/base/tui/editors/packages.nix

@@ -71,6 +71,7 @@
               requests
               pyquery
               pyyaml
+              toml # TOML writing; reading uses stdlib tomllib
               protobuf # protocol buffer compiler
             ]
           ))

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