docs: 将项目规范迁至 AGENTS.md 并保留 Claude 兼容入口

[lishuceo]

项目规范原先仅维护在 CLAUDE.md，CI 审查、技能模板和活动文档也硬编码该入口。本次将规范全文迁到 AGENTS.md，并让 CLAUDE.md 只保留一行 @AGENTS.md；后续规范维护统一修改 AGENTS.md。

保留 stub 有已验证的兼容原因：锁定的 Agent SDK 0.3.156 附带 Claude Code 2.1.156，低于原生加载 AGENTS.md 的 2.1.277 门槛。两个 claude-code-action@v1 workflow 使用网关且未固定 CLI 版本，不能用本机 2.1.283 的版本推断其能力。官方加载规则支持通过该导入方式共享指引。

• 更新两个 CI workflow、四个项目技能及其生成模板、README、活动计划和运行时提示词引用；其他目标仓库仍可使用 CLAUDE.md。
• 保留 SDK settingSources 默认值和调用方覆盖行为，包括 []；不升级依赖或改变权限、技能发现及工作区重启逻辑。
• PR 审查 workflow 将 --model opus 改为 --model anthropic/claude-opus-5-5，使用网关要求的完整模型标识。
• 研究和已完成计划保留历史引用；旧路由设计标注为历史方案。修正 session 文档中“CLAUDE.md 内容参与 prompt hash 并自动重置会话”的过时描述。

验证：

• git diff --check 通过。
• npm run typecheck 通过；npm run lint 无错误，202 条警告。
• npm run docs:check 及根目录 AGENTS.md / CLAUDE.md 的额外 Markdown lint 通过。
• 两个 workflow 的 YAML 解析通过；审查模型已按网关要求明确指定为 anthropic/claude-opus-5-5，模型修复通过结构比较确认仅改动这一项。
• 本地模拟 API 冒烟测试通过：SDK CLI 2.1.156 与 CLI 2.1.283 均通过 stub 加载 AGENTS.md；settingSources: [] 不加载项目指引。测试不调用真实模型。
• CI 同范围回归通过：TMPDIR=/var/tmp npx --no-install vitest run --exclude='**/quality.test.ts' --exclude='**/integration.test.ts'，100 个测试文件 / 1744 项测试全部通过。使用 /var/tmp 是为了避开本环境 /tmp/.git 对非 Git 目录用例的干扰；该干扰在未修改基线上也可复现。

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PR review: approved ✅

• Checked for my earlier inline comments (there were none)
• Read the PR intent and the full diff
• Compared the new AGENTS.md with the old CLAUDE.md, and checked the code, workflow, skill and doc references
• Posted the summary comment

I found no issues at confidence ≥75, so I left no inline comments.

• Migration is complete: all of the old CLAUDE.md text is now in AGENTS.md. The only additions are the compatibility section and the reworded settingSources gotcha. CLAUDE.md is now just @AGENTS.md.
• Design doc fix is correct: the session doc now says the system prompt hash is only used for logging. That matches src/claude/executor.ts:824-835, which only logs when the hash changes.
• Links and code: the anchor link resolves. settingSources behaviour is unchanged, including passing []. The src/ changes only touch comments and prompt text.

One optional suggestion, below the threshold: the reworded settingSources gotcha drops the old note that permissions.allow is checked before canUseTool. It's still useful to know when debugging blocked MCP tools, so consider keeping a line about it.

[github-actions]

✅ Approved

I found no issues at confidence ≥75. There were no earlier review comments of mine to resolve.

• Migration is complete: git diff origin/main:CLAUDE.md HEAD:AGENTS.md shows the full text was carried over. The only changes are a new Instruction Loading Compatibility section and a rewrite of the settingSources gotcha. The root CLAUDE.md is now just @AGENTS.md.
• Doc fix matches the code: docs/design/thread-session-mapping.md now describes systemPromptHash as diagnostic only. That matches src/claude/executor.ts:824-835, which hashes only knowledge plus the base prompt and just logs a message when the hash changes.
• Links resolve: AGENTS.md#instruction-loading-compatibility points at a real heading.
• settingSources behaviour is unchanged: settingSourcesOverride ?? [...] stays as it was, so passing [] still works. The src/ changes only touch comments and prompt text.
• Workflows: --model anthropic/claude-opus-5-5 is set in pr-review.yml.

Optional, below the threshold: the rewritten settingSources gotcha drops the old note that permissions.allow in project/local settings is checked before canUseTool. That's still useful to know when debugging MCP tools that get blocked. Consider keeping one line about it.

Overall: a careful, well-scoped docs migration.