Implement traverse-starter Phase 2 app registration

[enricopiovesan]

Summary

Wire up traverse-starter setup using traverse-cli app validate and traverse-cli app register so the app can be validated and registered into a local Traverse workspace.

Why

Specs 044 and 046 are both approved. This completes the traverse-starter integration from simple HTTP execute to full app bundle registration.

Definition of Done

• manifests/traverse-starter/app.manifest.json exists and is schema-valid
• traverse-cli app validate --manifest manifests/traverse-starter/app.manifest.json --json exits 0
• traverse-cli app register --manifest manifests/traverse-starter/app.manifest.json --workspace local-default --json exits 0
• Runtime loads registered workspace state
• UI can invoke registered workflow via HTTP API
• No fake registration path introduced

Governing specs

• 044-application-bundle-manifest (approved)
• 046-public-cli-app-registration (approved)

Depends on

#3 (runtime client), #9 (runtime pinned)