docs: add Node.js 22 requirement across skills

[pyramation]

Summary

Adds Node.js 22 as a documented requirement across four skill files. This was discovered while debugging pyramation-studio/agentic-db CI failures where Node.js 20 caused pnpm to resolve duplicate graphql module instances (16.13.0 and 16.13.1), producing "Cannot use GraphQLObjectType from another module or realm" runtime errors with PostGraphile/Graphile packages.

Files changed:

• constructive-setup/SKILL.md — New "Prerequisites" section with Node.js 22+ and pnpm 10+ requirements; new "Verify Node.js Version" as step 1 (renumbers subsequent steps)
• constructive-testing/SKILL.md — "Use Node.js 22+" added as Critical Rule skills for codegen #1
• pgpm/references/ci-cd.md — Workflow template updated from node-version: '20' → '22'; two new best practices added (Node.js 22 and --frozen-lockfile)
• constructive-tooling/references/pnpm-workspace.md — Compatibility updated from Node.js 18+ to Node.js 22+

Note: pgpm/SKILL.md already had Node.js 22+ in its compatibility field — this PR aligns the rest of the skills to match.

Review & Testing Checklist for Human

• Verify the Node.js 22 requirement is universal — This was observed in one repo (agentic-db with PostGraphile RC packages + pnpm overrides). Confirm this applies across all Constructive projects and not just specific dependency trees. If some projects work fine on Node 20, the wording should be softened.
• Check for Node 20 dependencies — Verify no Constructive projects or CI pipelines depend on Node 20-specific behavior that would break if agents switch to Node 22.
• Review the error description accuracy — The claim is "Node.js 20 causes different pnpm module resolution." Confirm this root cause explanation is correct vs. other factors (lockfile drift, missing pnpm.overrides, etc.).

Notes

• The --frozen-lockfile best practice was added to ci-cd.md as it was also instrumental in fixing the CI issue (prevents silent dependency drift between local and CI).
• The pgpm CI workflow template previously referenced node-version: '20' — agents copying this template would reproduce the exact issue we debugged.

Link to Devin session: https://app.devin.ai/sessions/342b041cb9ff4dcbaaba21b3141f69c5
Requested by: @pyramation

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