Add volunteer science provider catalog

[intel352]

Summary

• instantiate the public workflow-plugin-volunteer-science repo from the plugin scaffold
• add Folding@home upstream-client catalog metadata backed by workflow-plugin-compute-core/protocol
• declare workflow-plugin-compute-core as a plugin dependency and remove scaffold placeholders

Verification

• GOWORK=off go build ./...
• GOWORK=off go test ./... -v -race -count=1
• GOWORK=off go vet ./...
• GOWORK=off go run ./cmd/wfctl plugin validate-contract /Users/jon/workspace/workflow-plugin-volunteer-science (from /Users/jon/workspace/workflow)
• git diff --check