Add nbstripout pre-commit hook, keeping notebook outputs (#1372)

.pre-commit-config.yaml

@@ -33,6 +33,12 @@ repos:
     pass_filenames: false  # only run this check once globally per repo
     always_run: true
 
+- repo: https://github.com/kynan/nbstripout
+  rev: 0.8.1
+  hooks:
+  - id: nbstripout
+    args: [--keep-output]
+
 - repo: https://github.com/astral-sh/ruff-pre-commit
   rev: v0.9.10
   hooks:

docs/development.md

@@ -112,6 +112,20 @@ improved
 [complex numbers](https://optax.readthedocs.io/en/latest/api/contrib.html?complex-valued-optimization#complex-valued-optimization) support in Optax.
 
 
+## Pre-commit hooks
+
+The repository uses [pre-commit](https://pre-commit.com/) hooks, including
+nbstripout to normalize notebook metadata. nbstripout runs with
+`--keep-output`, so cell outputs and figures are preserved (they render in
+the docs); only execution counts and cell ids are normalized. To run the
+hooks locally:
+
+```bash
+pip install pre-commit
+pre-commit run --all-files
+```
+
+
 ## Contributor License Agreement
 
 Contributions to this project must be accompanied by a Contributor License