fix: align and verify supported Node releases

[rogerchappel]

Summary

• align the package engine range with the Node versions supported by runtime dependencies
• test Node 18.18, 20.9, 22, and 24 in CI
• install the packed tarball and invoke its CLI during package smoke testing
• document the supported Node release lines

Commit-by-commit changes

• fix: align Node engine support with dependencies — updates package and lockfile engine metadata
• test: smoke test the installed CLI package — packs, installs, and invokes the published CLI shape
• ci: test the supported Node release matrix — exercises the minimum and maintained Node releases
• docs: document supported Node releases — records the actual compatibility floor and excluded odd releases

Verification

• Tests or checks run: npm ci
• Tests or checks run: npm run package:smoke
• Tests or checks run: npm run release:check (71 tests passed; production audit, typecheck, lint, source smoke, and installed-package smoke passed)
• Tests or checks run: git diff --check origin/main...HEAD
• Manual review completed: workflow matrix, package metadata, changed files, and commit identity

Risk Level

• Low
• Medium
• High

Notes: The CI matrix is the cross-version verification; the same full release gate runs on Node 18.18, 20.9, 22, and 24.

Rollback Plan

• Revert the four commits to restore the previous engine declaration, single-version CI job, smoke check, and documentation.

Human Decision Needed

• None
• Maintainer review
• Product/design decision
• Security/privacy review
• Other: