Adopt registry_ref for traverse-starter process component (gated on registry seed + traverse #542/#548)

[enricopiovesan]

Summary

Switch the traverse-starter process component from local-path capability resolution to a registry reference, as the end-to-end demonstration that traverse-framework/registry actually serves a real Traverse app (publish -> sync -> resolve from the public tier).

Change: in manifests/traverse-starter/components/process/component.manifest.json, replace contract_path/wasm_binary_path/wasm_digest with registry_ref: {"namespace": "traverse-starter", "id": "traverse-starter.process", "version_range": "^1.0.0"} (exact schema per the traverse-side spec from traverse-framework/traverse#548).

This is explicitly gated — do not start until all of:

1. traverse-starter.process 1.0.0 is published in traverse-framework/registry (seed-publish ticket there)
2. traverse-cli registry sync exists (Implement traverse-cli registry sync traverse#542)
3. Dual-mode manifest loading (contract_path xor registry_ref) is implemented traverse-side (Spec: public-scope reconciliation + registry_ref resolution (feeds #542/#543) traverse#548 spec + implementation)

Note: nothing in reference-apps breaks in the meantime — the settled design keeps contract_path fully valid (dual mode); this flip is a demonstration, not a migration forced by a breaking change.

Governing Spec

• Governed by the traverse-side spec produced under Spec: public-scope reconciliation + registry_ref resolution (feeds #542/#543) traverse#548 and registry spec 006-public-scope-and-identity; no reference-apps-local spec required beyond following the manifest schema those define.

Definition of Done

• Process component manifest uses registry_ref (no contract_path/wasm_binary_path/wasm_digest)
• registry sync + app registration resolves the capability from the synced public tier, WASM fetched into the local digest-verified cache at registration time
• The app's existing smoke flow (traverse_starter_example_smoke evidence path) passes unchanged
• No live network access at execution time (constitution)

Test plan

• Fresh workspace: traverse-cli registry sync, register the app, run the starter flow end to end; verify output unchanged vs the contract_path version
• Negative: registration without prior sync fails with the actionable "sync required" error
• Digest check: cached WASM digest equals sha256:5647c39a1d25d8728350f9619025292a62e78a602068a2ad9b6f075751c93d99