[Repo Assist] ci(docs): pin Poetry 2.1.3 and add venv caching to docs-ci.yml

[github-actions]

🤖 This PR is created by Repo Assist, an automated AI assistant.

Problem

docs-ci.yml had two inconsistencies compared to the rest of the CI ecosystem:

1. Unpinned Poetry installation: python3 -m pip install poetry installs whatever the latest Poetry release is. Every other workflow (ci.yml, nightly-tests.yml, advanced-on-demand.yml) pins Poetry to 2.1.3 via abatilo/actions-poetry@v4.0.0. A new Poetry major/minor release could silently break the docs build without touching any code.

2. No virtualenv caching: every docs-CI run performed a full poetry install -E plotting -E pydot -E pygraphviz -E econml --with docs, which takes ~4 minutes. ci.yml already caches the .venv keyed on poetry.lock; docs-CI was missing this.

3. No workflow_dispatch trigger: maintainers had no way to trigger a docs build manually without opening a dummy PR or pushing to an existing PR.

Changes

	Before	After
Poetry install	pip install poetry (latest)	abatilo/actions-poetry@v4.0.0 @ 2.1.3
Virtualenv	Fresh every run	Cached by poetry.lock hash
Manual trigger	Not available	workflow_dispatch added

Trade-offs

• Uses the same abatilo/actions-poetry@v4.0.0 action already trusted by the other workflows — no new action introduced.
• Cache key is venv-docs-py3.9-<lock-hash>, separate from the main CI keys (which include python-version and os), so there's no cross-contamination.
• The Install Python Dependencies step is skipped on cache hit, matching ci.yml's pattern exactly.

Test Status

This is a CI workflow change only; no Python code was modified. The change will be validated the first time it runs on a PR.

Generated by 🌈 Repo Assist, see workflow run. Learn more.

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@11c9a2c442e519ff2b427bf58679f5a525353f76

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Warning

Protected Files — Push Permission Denied

This was originally intended as a pull request, but the patch modifies protected files. A human must create the pull request manually.

Protected files

• .github/workflows/docs-ci.yml

The push was rejected because GitHub Actions does not have workflows permission to push these changes, and is never allowed to make such changes, or other authorization being used does not have this permission.

Create the pull request manually

# Download the patch from the workflow run
gh run download 29839969101 -n agent -D /tmp/agent-29839969101

# Create a new branch
git checkout -b repo-assist/eng-docs-ci-pin-poetry-cache-20260721-641832eb1f885cc0 main

# Apply the patch (--3way handles cross-repo patches)
git am --3way /tmp/agent-29839969101/aw-repo-assist-eng-docs-ci-pin-poetry-cache-20260721.patch

# Push the branch and create the pull request
git push origin repo-assist/eng-docs-ci-pin-poetry-cache-20260721-641832eb1f885cc0
gh pr create --title '[Repo Assist] ci(docs): pin Poetry 2.1.3 and add venv caching to docs-ci.yml' --base main --head repo-assist/eng-docs-ci-pin-poetry-cache-20260721-641832eb1f885cc0 --repo py-why/dowhy

Generated by 🌈 Repo Assist, see workflow run. Learn more.

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@11c9a2c442e519ff2b427bf58679f5a525353f76