use uv for script reproducibility

Author: tswast

packages/bigframes/specs/bigframes-bigquery-generator.md

@@ -16,6 +16,40 @@ through all the same yaml files and checks that the functions have been included
 in the `bigframes.bigquery` module, as the `__init__.py` file requires manual
 updates.
 
+## Running the generator
+
+Since the dependencies for the script differ from that of bigframes
+and its test suite, use the self-contained Python script technique described at
+https://docs.astral.sh/uv/guides/scripts/
+to automatically manage dependencies using `uv`. Therefore, the header of the
+script will look something like:
+
+```python
+#!/usr/bin/env -S uv run --script
+#
+# /// script
+# dependencies = [
+#   "jinja2",
+#   "pyyaml",
+# ]
+# ///
+#
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# ...
+```
+
+To run the script:
+
+```bash
+cd packages/bigframes
+uv run scripts/generate_bigframes_bigquery.py
+```
+
+To improve reproducibility, we also check in the uv lock file generated by
+running `uv lock --script scripts/generate_bigframes_bigquery.py`.
+
 ## Generated code organization
 
 The `generate_bigframes_bigquery.py` script generates submodules of
@@ -31,6 +65,11 @@ to the `bigframes.bigquery._operations.builtins.bit` submodule.
 Each generated module has all functions defined in the YAML file converted to
 the equivalent Python definition, including keyword arguments and docstrings.
 
+### Code generation
+
+The code will be templated using the jinja2 template engine. This allows
+proposed changes to the templated code to be reviewed more easily.
+
 ### Handling optional arguments
 
 When the user calls a Python function without specifying the optional