The Codex and Claude Code subagent providers were production dependencies of
@deepseek-ai/dsh-base and mounted by its Cordis composition, so every install of
the base bundle carried two providers that only some products want.
Drop both from the base bundle's dependencies and composition. The examples keep
them as explicit dependencies, base's tests lock their absence, and the product
preset e2e mounts the providers it needs explicitly.
Cherry-picked from #2387 (two commits squashed into one).
