[ychampion]

A fresh npm install primeng@18.0.2 can select Angular common 19 alongside core 18, then fail with ERESOLVE even though common 18 satisfies the peer group.

When a missing required peer has no direct constraint on its virtual parent, consult a sibling peer constraint before recursively loading the candidate’s own peers.
Reuse the existing two-edge version selection, retaining direct-parent priority and the skip for absent optional peers.

Fixes #10054.

Validation:

• Reduced dependency-graph regression fails before the fix and passes after.
• Two optional-peer owners do not trigger a fetch for an absent provider; removing the guard makes this strict-mock regression fail.
• Fresh public-registry PrimeNG lockfile-only and full installs pass, all Angular packages resolve 18.2.14, and npm ls --all --json reports no problems.

Full validation: node . run test-all executed the CLI, docs, smoke tests and all workspaces.
The initial run hit Arborist’s chmod/EACCES assertion because this session runs as root, plus a 30-second file timeout in libnpmexec; the other suites passed.
Rerunning the full Arborist suite with DAC bypass capabilities removed and the full libnpmexec suite with a 120-second timeout passed, each with 100% coverage and lint/template checks.

Assisted by AI.