docs(product): position LoopX as the layer on top of agent harnesses

[huangruiteng]

Summary

Adopt one consistent product definition across the repo's first-screen surfaces:
LoopX runs on top of different agent harnesses (Codex App, Codex CLI, Claude
Code, Cursor, dsh, or your own runner) and provides long-horizon state,
semantic decisions, governance, recovery, and human-agent collaboration.

• README.md / README.zh-CN.md: hero subtitle, intro paragraph, and a
  promise-mapping sentence above the five-question capabilities table.
• docs/product/vision.md: product vision paragraph and First-Screen Copy
  candidates.
• docs/product/core-control-plane/README.md: one-line positioning blockquote
  linking to the product vision.
• apps/presentation/site/src/App.tsx: English and Chinese frontstage hero
  body.

The existing control-plane mechanism language is preserved; the new definition
states where LoopX sits (above harnesses) and what it provides, while the
five-question table keeps the promise concrete.

Validation

• npm run build passes for apps/presentation/site (tsc + vite).
• examples/frontstage-pages-workflow-smoke.py passes.
• loopx check --scan-path reports a clean public boundary for all five
  changed files.
• git diff --check clean; English and Chinese hero text verified in a local
  production build.

Review Notes

• "agent harness" is used deliberately (rather than bare "harness") to avoid
  collision with the internal effect-interpreter usage of "harness" in the
  control-plane course docs.
• First-screen hero changes: rendered previews are shared with the requester
  outside this PR; please review the first viewport before merge.

[huangruiteng]

Approval conclusion (author-owned PR; GitHub blocks formal self-approval)

详细中文评审：把 LoopX 定位为 agent harness 之上的控制面层（PR #3202）

评审目标 head：9d43d13982863c79ce87aba27dd1514ae7e83fde（base: main，2 个 commit，5 个文件，+35/-12）

动机

随着 #3188（dsh connector）和 #3201（dsh 控制面适配器文档）进入公开叙事，README/vision 里"LoopX 是 provider-neutral 控制面"的旧表述没有明确回答"它和 Codex/Claude Code/Cursor/dsh 是什么关系"。本 PR 把定位收敛成一句话：LoopX 运行在 agent harness 之上，而不是替代它们——harness 负责有界执行，LoopX 提供长程状态、语义决策、治理、恢复与人机协同。这是对既有事实的准确描述，也是把 connector 文档和产品定位统一起来的正确一步。

改动思路

改动分三层：README（英文+中文）的 hero/正文/能力表改为"harness 之上"框架，并给五个问题各配一个产品承诺（目标→长程状态、下一步→语义决策、人类判断→人机协同、证据→恢复、能否继续→治理）；docs/product/vision.md 与 docs/product/core-control-plane/README.md 同步同一句话；站点 frontstage hero（App.tsx）改英文/中文 body 文案。没有运行时改动，CI build ×2 与 dependency-review 已绿。

具体改动

• README.md（+11/-5）、README.zh-CN.md（+8/-4）：hero 副标题、简介段落、Capabilities 引入句。
• docs/product/vision.md（+9/-1）、docs/product/core-control-plane/README.md（+5）：产品愿景与核心图集的 positioning 一致化。
• apps/presentation/site/src/App.tsx（+2/-2）：frontstage hero 中英文 body 更新。

关键内容讲解

1. README hero 副标题："LoopX runs on top of Codex App, Claude Code, Cursor, dsh, or your own agent harness, providing long-horizon state, semantic decisions, governance, recovery, and human-agent collaboration — objectives, gates, todos, evidence, quota, and handoffs stay stable while the harness executes bounded turns." 这准确复用了 #3188/#3201 建立的分层边界（harness 执行、LoopX 治理），且没有声称任何未实现的能力。
2. 五个问题→产品承诺的映射是新增的最有价值内容：把抽象的 control-plane 机制翻译成用户可感知的 promise，中英文一致。
3. vision.md 与 core-control-plane README 的 positioning callout 与 README 完全同句，避免文档漂移。

对主干的风险

• 首次屏审查门（P1，流程项）：本 PR 同时改了 README 的第一屏 hero/简介和站点 frontstage hero（App.tsx）。按仓库 AGENTS.md 的 First-Screen Review Gate，合入前需要向用户展示预览（README 首屏 + 站点 hero 的截图/本地 URL）并取得确认。作为评审我把这个 gate 显式记录下来；由于这是 owner 自建 PR，owner 可在合并前自行完成预览确认。
• 无运行时行为变化；文案与既有 connector/架构文档一致，没有超卖（与 #3201 的问题相反）。
• 轻微（P2）：英文 hero 副标题一行偏长，在窄屏可能换行不均匀；非阻塞。

我的整体评价

定位准确、中英文一致、与已合并的 harness 类文档同源，把"LoopX 和 agent harness 的关系"从模糊变成明确。唯一需要执行的是首次屏审查门（预览确认后再合并）。结论：APPROVE。

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English Verdict (PR #3202)

• Exact head reviewed: 9d43d13982863c79ce87aba27dd1514ae7e83fde
• Verdict: APPROVE (author-owned PR; GitHub blocks formal self-approval, recorded as COMMENTED)
• Key finding: The PR accurately repositions LoopX as the layer on top of agent harnesses (Codex App/CLI, Claude Code, Cursor, dsh, or your own runner) and maps the five control-plane questions to product promises, with consistent EN/ZH copy across README, vision, and the frontstage hero. No runtime changes; build and dependency-review are green.
• Process note (P1): because this changes the README first screen and the site hero, the repo's First-Screen Review Gate requires a user-visible preview and explicit approval before merge — the owner should complete that before merging. Minor P2: the English hero subtitle is long for narrow screens.