fix: use Node.js 22 in Nix flake

[leno23]

Summary

• update the Nix package build inputs from nodejs_20 to nodejs_22
• update the dev shell Node runtime to nodejs_22 as well

Why

Node.js 20 is now marked insecure in nixpkgs after reaching EOL, which causes Nix evaluation/builds to fail for OpenSpec users.

Fixes #1119.

Validation

• Confirmed flake.nix no longer references nodejs_20
• Not run: nix build, because Nix is not installed in this local environment

Summary by CodeRabbit

• Chores
  • Updated Node.js runtime to version 22 for build and development environments.
  • Updated CI workflows to use Node.js 22 for testing, linting, type-checking, and release validation.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 2326c87e-34d9-48a0-9770-86c5a4c62f73

📥 Commits

Reviewing files that changed from the base of the PR and between d44fc58 and 8494c88.

📒 Files selected for processing (1)

• .github/workflows/ci.yml

✅ Files skipped from review due to trivial changes (1)

• .github/workflows/ci.yml

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📝 Walkthrough

Walkthrough

Replaces Node.js 20 with Node.js 22 in the Nix flake (build and dev shell inputs) and in GitHub Actions workflow job configurations.

Changes

Node.js Version Update

Layer / File(s)	Summary
Bump Node.js in flake (build + dev shell) flake.nix	nativeBuildInputs for packages.default and devShells.default.buildInputs switch from nodejs_20 to nodejs_22.
Bump Node.js in CI workflow jobs .github/workflows/ci.yml	All actions/setup-node entries in test, lint, and validate-changesets jobs now use node-version: '22' instead of '20'.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• TabishB

Poem

🐰 I hopped from twenty, light and spry,
To twenty-two beneath the sky,
Builds hum along, CI sings too,
A cozy bump — a rabbit's view. 🥕

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: updating Node.js from version 20 to 22 in the Nix flake configuration.
Linked Issues check	✅ Passed	The PR successfully addresses issue #1119 by replacing nodejs_20 with nodejs_22 in flake.nix, eliminating the insecure package error and restoring Nix build functionality.
Out of Scope Changes check	✅ Passed	The PR includes changes to both flake.nix and GitHub Actions workflow (.github/workflows/ci.yml), with the workflow updates being necessary and related to maintaining CI consistency with the Node.js version upgrade.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

flake.nix (1)

58-58: ⚡ Quick win

Update specification document to reflect Node.js 22.

The Nix flake support specification at openspec/changes/archive/2026-01-07-add-nix-flake-support/specs/nix-flake-support/spec.md (lines 47-73) explicitly states "The system SHALL use Node.js 20 as specified in package.json engines field" and references nodejs_20 in scenarios. This documentation is now outdated and inconsistent with the actual implementation.

Update the spec document to reflect the Node.js 22 requirement.

Also applies to: 100-100

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@flake.nix` at line 58, The spec currently asserts "The system SHALL use
Node.js 20" and references nodejs_20; update the specification text and all
scenario references to reflect Node.js 22 by replacing "Node.js 20" and
nodejs_20 with "Node.js 22" and nodejs_22, and also update any mention of the
package.json engines field to match Node.js 22 so the document aligns with the
flake change (nodejs_22).

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@flake.nix`:
- Line 58: The CI workflow uses Node.js 20 while the flake uses nodejs_22;
update the GitHub Actions workflow (.github/workflows/ci.yml) to match by
changing the setup-node/node-version or matrix value from 20 to 22 so CI and the
Nix flake (nodejs_22) use the same Node.js version consistently.

---

Nitpick comments:
In `@flake.nix`:
- Line 58: The spec currently asserts "The system SHALL use Node.js 20" and
references nodejs_20; update the specification text and all scenario references
to reflect Node.js 22 by replacing "Node.js 20" and nodejs_20 with "Node.js 22"
and nodejs_22, and also update any mention of the package.json engines field to
match Node.js 22 so the document aligns with the flake change (nodejs_22).

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: 816f47f5-af50-4751-8390-2c02c2683a8b

📥 Commits

Reviewing files that changed from the base of the PR and between 1b06fdd and d44fc58.

📒 Files selected for processing (1)

• flake.nix