Add Phase 2 smoke test to nightly CI when runtime is available

[enricopiovesan]

Summary

Extend .github/workflows/nightly.yml to run scripts/ci/phase2_smoke.sh when a Traverse runtime is reachable (via repo variable/secret or self-hosted runner).

Why

Phase 1 smoke runs nightly today, but Phase 2 app registration validation (phase2_smoke.sh) only runs manually. Regressions in manifest validation or registered capability invocation would not be caught automatically.

Depends on

• scripts/ci/phase2_smoke.sh (exists)
• Issue Fix phase1_smoke.sh: wrong capability ID and input field name #84 (phase1_smoke alignment) recommended first

Blocked by

• Hosted runtime availability: needs TRAVERSE_RUNTIME_URL and/or TRAVERSE_REPO secret configuration on the org/repo
• Decision on whether nightly spins up runtime or uses persistent hosted instance

Definition of Done

• Nightly workflow runs bash scripts/ci/phase2_smoke.sh when runtime env is configured
• Job skips gracefully with clear message when runtime secrets/vars absent (same pattern as phase1 skip)
• docs/quality-standards.md Nightly CI section documents Phase 2 coverage
• Document required GitHub Actions vars/secrets for maintainers

Validation

• Manual workflow_dispatch with runtime configured → Phase 2 smoke PASS
• Without runtime vars → job skips without failing the workflow