ci: group dependabot updates by semver level and skip npm majors

[derogab]

Summary

Group Dependabot updates by semver level to reduce maintenance noise while keeping breaking npm upgrades manual.

Changes

• Group GitHub Actions updates into separate major, minor, and patch pull requests.
• Group npm minor and patch updates into separate pull requests.
• Ignore npm major updates.

Test plan

• Validate the Dependabot YAML structure.
• Run git diff --check.
• Confirm the next monthly run creates the expected grouped updates.

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Summary by cubic

Configure Dependabot to group updates by semver and skip npm majors to reduce PR noise and keep breaking upgrades manual.
github-actions PRs are split into major/minor/patch groups; npm minor and patch updates are grouped; npm major updates are ignored.

^{Written for commit e0659d1. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}