* refactor(env): unify node version specifier parsing into parseNodeSpecifier in node.resolver
Move parseNodeSpecifier from @pnpm/plugin-commands-env to @pnpm/node.resolver and
replace the simpler parseEnvSpecifier with an enhanced version that supports all
Node.js version specifier formats: standalone release channels (nightly, rc, test,
v8-canary, release), well-known aliases (lts, latest), LTS codenames (argon, iron),
semver ranges (18, ^18), and channel/version combos (rc/18, nightly/latest).
* fix(env): address parseNodeSpecifier review feedback
- Remove overly strict release/X.Y.Z-only validation; release/latest,
release/lts, and release/<range> are now accepted
- Validate unknown release channels (e.g. foo/18) with a clear error
instead of letting them fall through to a confusing network failure
- Add test cases for release/latest, release/lts, and release/18
