feat(python): manage python with uv via nix-ld

modules/home.nix

@@ -89,6 +89,10 @@ in
     PYTHONIOENCODING = "UTF-8";
     PYTHONSTARTUP = "${config.xdg.configHome}/python/startup";
     PYTHON_HISTFILE = "${config.xdg.cacheHome}/python/history";
+    # Default interpreter uv picks for `uv run`/`uv venv` without an explicit
+    # -p. Pins throwaway REPLs and new projects to one version across machines
+    # (further steered by uv.toml below). Fetched on demand by uv, not Nix.
+    UV_PYTHON = "3.14";
     # psql / wget / readline configs, XDG-routed (the rc files are declared
     # via xdg.configFile below).
     PSQLRC = "${config.xdg.configHome}/psql/rc";
@@ -123,6 +127,8 @@ in
     # finalPackage) — do NOT also list it here, or buildEnv conflicts on the
     # wrapper binary.
     nodejs
+    uv          # Python: versions, venvs, deps, lockfile. Runs uv-managed
+                # standalone CPython via nix-ld (see modules/nixos.nix).
     highlight   # `ccat` alias: syntax-highlighted cat
     jq          # JSON on the command line (scripts, ad-hoc inspection)
     libreoffice
@@ -144,6 +150,13 @@ in
   xdg.configFile = {
     "python/startup".source = ./assets/python-startup.py;
 
+    # uv global config. "managed" = always use uv's own CPython, never a
+    # system/Nix python — keeps behaviour reproducible regardless of what else
+    # is on PATH. Default version comes from UV_PYTHON above.
+    "uv/uv.toml".text = ''
+      python-preference = "managed"
+    '';
+
     # psql: unlimited, per-database history file (kept out of $HOME).
     "psql/rc".text = ''
       \set HISTFILE ${config.xdg.cacheHome}/psql/history-:DBNAME
@@ -325,6 +338,8 @@ in
       g = "git";
       e = editor;
       v = editor;
+      # Throwaway REPL/scripts as if `python` were global; resolves to UV_PYTHON.
+      python = "uv run python";
     };
 
     # Interactive bits with no first-class HM option: prompt, autocd,