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

[shubhangithub]

Fixes #1372. Re-lands #1519, which had all 13 CI checks green (including pre-commit run -a) and a review of "once the CI passes, I'll be happy to merge", but was closed by its author. The hook config here is byte-identical to that PR's final state.

• .pre-commit-config.yaml: nbstripout 0.8.1 with --keep-output, so cell outputs and figures survive (they render in the docs).
• One-time normalization of the 20 notebooks under docs/ and examples/ (one notebook was added since Feat: Add pre-commit hook that strips notebooks of metadata #1519).
• A short pre-commit note in docs/development.md (corrected from Feat: Add pre-commit hook that strips notebooks of metadata #1519's version, which said outputs are stripped — with --keep-output they aren't).

Keep-outputs verification, comparing parsed JSON before vs after for all 20 notebooks: cell sources identical, output payloads identical, image/png counts identical (e.g. freezing_parameters.ipynb 18 outputs / 12 images, unchanged). The normalization changes two things: execution_count set to null (112 cells, 5 execute_result outputs), and cell ids renumbered to sequential integers in the three notebooks that carry them (muon, rosenbrock_ademamix, linear_assignment_problem) — standard deterministic nbstripout behavior, same as #1519's config produced. The rest of the notebook diff is nbformat's standard reindentation.

pre-commit run --all-files (idempotent on second run) and ruff check . (pinned v0.9.10) pass clean locally.

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