[intel352]

Summary

• scaffold public workflow-plugin-compute-container plugin repo
• add reusable sandboxed command and sandboxed container-build runtime adapter APIs
• publish runtime adapter metadata through plugin.json runtimeAdaptersRef and runtime-adapters.json
• add conformance coverage for env ref resolution, stripped runtime payloads, artifact hashing, reserved build env rejection, symlink path rejection, digest marker handling, and multi-tag forwarding

TDD / verification

RED examples observed before fixes:

• GOWORK=off go test ./container -run TestSandbox -count=1 failed with undefined adapter APIs
• GOWORK=off go test ./container -run TestRuntimeAdapterContracts -count=1 failed with undefined contract builders
• GOWORK=off go test ./container -run 'Test(ContainerBuildRejectsReservedControlEnvOverride|ContainerBuildPassesAllTagsAsJSON|CommandArtifactHashRejectsSymlinkPathComponents)' -count=1 failed for accepted reserved env, missing WORKFLOW_COMPUTE_BUILD_TAGS, and symlink artifact traversal\n\nGREEN after implementation:\n- GOWORK=off go test ./... -count=1\n- GOWORK=off go vet ./...\n- GOWORK=off go build ./...\n- wfctl plugin validate-contract .\n\n## Notes\nwfctl plugin validate-contract currently recognizes module/step/trigger/service_method/message contract kinds only. Runtime adapter discovery is therefore exposed via runtimeAdaptersRef rather than an unknown plugin.contracts.json kind.\n\nPart of workflow-compute RTE-1 / T520. Host-only task admission, leases, authz, credential resolution, registry allowlists, proof/reward mutation, and worker binding remain outside the plugin.