Add Dependabot for GitHub Actions and grouped security updates

[silveltman]

What changed

Adds .github/dependabot.yml with two entries:

• github-actions: weekly, all actions grouped into one PR. Dependabot updates the SHA pins and their version comments together.
• npm: version update PRs off (open-pull-requests-limit: 0), every security update grouped into one PR (applies-to: security-updates, pattern *).

Why

The workflows pin actions to commit SHAs, which go stale without automation. Dependabot security updates are being turned on for active repositories; grouping keeps each repository to one PR per kind, which fits the Actions budget. The silveltman pilot showed Dependabot handles the pnpm 12 lockfile, and the liquid run showed the grouped SHA and version comment update.

Verification

• Syntax per the GitHub Dependabot options reference; same entries as the merged silveltman and liquid configs.
• Check runs the repository's formatter over the new file.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • Automated maintenance checks for GitHub Actions now run weekly, and related update pull requests are grouped together. Security update pull requests are also grouped to make them easier to review.
  • These maintenance changes do not alter the app’s features or how it behaves for end users.

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📝 Walkthrough

Walkthrough

The change adds Dependabot version 2 configuration. It schedules weekly checks for GitHub Actions and npm dependencies. It groups GitHub Actions updates and npm security updates. It sets the npm open pull request limit to zero.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Other

Merge Risk: 🟡 Moderate · up to 14a2f

Grouped npm security updates may not be created. Confirm a supported update mechanism before merging.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 14a2f

The configuration schedules and groups update proposals without directly changing credentials, workflow permissions, or executable dependencies. Accepted updates can affect privileged release automation, so merge controls remain important. Those external controls could not be verified; no introduced security defect was established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — A compromised upstream Action accepted through an update proposal could execute in existing release automation with repository write and identity-token permissions. The release workflow also consumes a GitHub App private key and uses the resulting token. These authorities predate this PR; the configuration does not itself bypass the merge boundary. The App's wider installation scope is unverified.

Trust Boundaries and Controls

• observed — Existing CI tests pull requests targeting main with contents-read-only permission, SHA-pinned Actions, disabled checkout credential persistence, and installation scripts and pnpmfiles suppressed. These controls constrain proposal testing but do not establish that successful CI or approval is required before merge.

Resilience and Maintainability Implications

• inferred — Grouping security updates can couple remediation progress: an incompatible member may delay acceptance of other fixes in the proposal. The configuration alone does not establish that such blocking occurs or how failed groups are recovered.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding Dependabot for grouped GitHub Actions updates and npm security updates.
Description check	✅ Passed	The description explains the Dependabot configuration, update policies, rationale, and verification steps. It is directly related to the changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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🤖 Prompt to fix review comments

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Inline comments:
Review comments at @.github/dependabot.yml:
- Line 15: Update the npm ecosystem configuration in Dependabot to use a pnpm
version it supports or an alternative supported security-update mechanism, so
dependency graph processing and grouped security-update PRs work with the root
package’s pnpm requirement.

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: Organization UI
• Review profile: CHILL
• Plan: Advanced
• Run ID: 332d65e3-3705-4be3-b126-6bf30fc2f2f9

📥 Commits

Reviewing files that changed from the base of the PR and between 678a4a9 and 14a2fea.

📒 Files selected for processing (1)

• .github/dependabot.yml

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