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Reorganize along Problem / Proposal / High-level API / Detailed design / Roadmap / FAQ / Prior art / Alternatives / Acceptance / Risks. The product survey and Pi failure shapes move to Prior art; user-facing behavior (walkthrough, cordis.yml config, stdio, ACP, ctx.modes) gets its own High-level API section; FAQ collects behavioral clarifications of the chosen design, disjoint from Alternatives (rejected designs) and Risks (accepted costs). The zh counterpart and its pairing metadata are removed; the RFC is English-only (not in the required-pairs manifest).