ci: security-only Dependabot for pip + weekly poetry.lock update job

[blink1073]

References

None

Description

Splits dependency updates into two lanes: Dependabot now only opens PRs for pip security fixes (routine version bumps are disabled via open-pull-requests-limit: 0), while a new weekly cron workflow batches routine version bumps into a single poetry.lock update PR using calysto/maintainer_tools's poetry-lock-update composite action (with a 7-day minimum release-age cooldown).

Changes

• .github/dependabot.yml: add open-pull-requests-limit: 0 to the pip entry so only security-update PRs are opened automatically.
• .github/workflows/lock-update.yml: new weekly (Monday 6am) cron workflow that runs poetry update --lock via calysto/maintainer_tools/actions/poetry-lock-update@v1 and opens a batched, maintenance-labeled PR when the lock file changes. Modeled on the existing pre-commit-autoupdate.yml pattern (pinned checkout, persist-credentials: false, environment: release, fork-safety guard).
• pyproject.toml / poetry.lock: split [dependency-groups] arrays (dev, test-all, coverage, typing) that mixed plain strings with include-group tables into homogeneous arrays. Mixed arrays crash Dependabot's Poetry (toml-rb) resolver. No dependency resolution changes — poetry.lock diff is group-membership metadata only.

Backwards-incompatible changes

None

Testing

• just typing — passes
• just pre-commit — all hooks pass, including poetry-check/poetry-lock/actionlint
• just test — 487 passed, 68 skipped
• Verified poetry.lock resolves identically (no version changes) after the dependency-groups split
• New workflow YAML validated via actionlint (pre-commit) and checked against zizmor for parity with the existing pre-commit-autoupdate.yml workflow

AI usage

• Some or all of the content of this PR was generated by AI.
• The human author has carefully reviewed this PR and run this code.
• AI tools and models used: Claude Code (Sonnet 5)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.54%. Comparing base (c7d512f) to head (c62742d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #467   +/-   ##
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  Coverage   93.54%   93.54%           
=======================================
  Files          51       51           
  Lines        2974     2974           
  Branches      416      416           
=======================================
  Hits         2782     2782           
  Misses        131      131           
  Partials       61       61           

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