docs(rfc): define minimal Topic Memory recovery storage

[knqiufan]

Which issue or RFC does this PR close?

Related to #1885; defines the recovery storage design for implementation PR #1966. This documentation PR does not close the bug.

Rationale for this change

A blocked Topic frontier needs durable diagnosis and explicit recovery. A retry receipt is necessary for idempotency, but does not establish a need for permanent history of every successful or failed attempt. The storage lifecycle and reuse boundary need agreement before the implementation is merged.

What changes are included in this PR?

• Add matching English and Chinese RFCs proposing current-attempt metadata in the existing budget and one Topic-owned terminal-block table with an acceptance receipt in the same row.
• Assess processing/intents/lease and Artifact reuse, including transaction feasibility, permissions, lifecycle restrictions and cleanup.
• Define exact attempt versus cumulative ranges, atomic retry, replay after restart or disabled processing, indefinite block/receipt retention, and offline migration requirements.
• Include isolated synthetic SQLite storage sizing and an explicitly hypothetical growth example, plus implementation acceptance criteria.

Are there any user-facing changes?

Design documentation only; no runtime, API, generated code or schema changes. The proposed implementation adds authorized status/block/retry operations and requires an explicit offline schema upgrade. Unknown legacy selected ranges remain nullable. Implementation PR #1966 stays draft pending design agreement.

How was this change tested?

• uv sync --locked.
• pnpm --dir website lint and pnpm --dir website test: passed.
• pnpm --dir website build: documentation generation, link validation, static build and export verification passed.
• uv run --no-sync ty check --python-platform linux: passed.
• git diff --check and manual UTF-8, bilingual contract-field and relative-link checks: passed.
• uv run --no-sync prek run -a: formatting/lint hooks passed; the default Windows ty-check reports existing POSIX API attributes in unchanged native-code sources. Document-file hooks passed with that unrelated check excluded.
• Synthetic SQLite sizing covers isolated table layouts, not runtime performance, a live model, OceanBase, seekDB or native host acceptance. Runtime tests are not claimed for this documentation change.

AI usage statement

OpenAI Codex assisted the bilingual RFC, source inventory, design review, synthetic storage sizing and documentation validation.