feat(agents): add TanStack Start control plane

[gregkonush]

Summary

• Migrates services/agents from the custom Bun/H3 control-plane web surface to a TanStack Start app on Bun with Vite 8, React 19, Tailwind CSS v4, and shadcn UI.
• Adds a generated primitive registry from charts/agents/crds/*.yaml, schema-form create flows, primitive overview/list/detail routes, breadcrumbs, and server-side typed-resource create/list/get APIs.
• Preserves existing /health, /ready, /mcp, /metrics, and /v1/* paths by delegating TanStack Start server routes to the existing Agents runtime, while keeping agents-controllers separate.
• Documents the control-plane UI architecture, route model, create flow, smoke-test expectations, and chart exposure.

Related Issues

None

Testing

• bun run --cwd services/agents test
• bun run --cwd services/agents tsc
• bun run --cwd services/agents lint
• bun run --cwd services/agents build
• scripts/agents/validate-agents.sh
• bun run lint:argocd
• mise exec helm@3 -- kustomize build --enable-helm argocd/applications/agents >/tmp/agents-render.yaml && wc -l /tmp/agents-render.yaml
• Browser Use QA against the local dev server verified / redirect, all primitive list routes, detail/create routes, breadcrumbs, responsive layout, and a disposable Signal create/detail flow.
• Computer Use QA against Chrome visually verified the operator shell, sidebar primitives, breadcrumbs, schema form, manifest preview, and create button.

Screenshots (if applicable)

N/A

Breaking Changes

None

Checklist

• Testing section documents the exact validation performed (or N/A with justification).
• Screenshots and Breaking Changes sections are handled appropriately (removed or filled in).
• Documentation, release notes, and follow-ups are updated or tracked.