feat(frontend): add slim architecture skeleton

[xyh202131]

Summary

• reduce the frontend architecture PR to coarse module docs, entity data contracts, and public API interfaces only
• keep WorkflowController as one shared workflow interface instead of splitting next/restart/interruption into submodules
• remove package/dependency/CI wiring, React route/page/feature placeholders, config files, and interface-vs-implementation mechanisms

Scope intentionally excluded

• no package.json or lockfile
• no CI, tests, build config, Vite, TS config, or lint/format config
• no React page shells, feature placeholder components, app entry, CSS, mocks, adapters, repositories, ports, services, or dependency injection
• no implementation of server calls or workflow state transitions

Validation

• reviewed the diff against Yang Hanxing's feedback: only interfaces/data contracts and architecture docs remain
• searched the PR content for adapter/repository/port/mock/production/composition/package/npm/vite/tsconfig/React implementation markers

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Project	Deployment	Actions	Updated (UTC)
windup	Error		Jul 30, 2026 5:01am

[xyh202131]

Closing in favor of the continued frontend module-boundary review path.