Add `parallel-steps` rule: check wait/cancel references and steps allowed inside `parallel`#695

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devantler wants to merge 9 commits into

devantler:parallel-steps-id-refs

Commits on Jun 25, 2026

Add support for parallel steps (background, wait, wait-all, cancel, parallel)

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Make `cancel` take a single step ID per the spec

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Commits on Jun 26, 2026

Flag `wait-all` with arguments and combined `wait`/`wait-all`

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Add `parallel-steps` rule to check `wait`/`cancel` step references

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Simplify parallel-steps rule to reuse the visitor's step traversal

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Reject `parallel` step nested in another `parallel` step

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Test parallel-steps rule against expression-valued background and refs

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Reject background/wait/cancel/nested-parallel inside a `parallel` group

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Report a forbidden `parallel`-group step once, without a reference cascade

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