chore: bootstrap project scaffolding

Add architecture doc (research-wiki/ARCHITECTURE.md), CLAUDE.md with
tiered SOP for Fable 5, adapted .claude skills/hooks/settings, package
skeleton (src/polygateway), pyproject with import-linter contracts,
Makefile, .env.example and smoke test.

.claude/templates/EXPERIMENT_PLAN_CN.md

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+# 实验计划模板
+
+> 用于把 claim、实验块、运行顺序和资源预算拆成可执行计划。
+
+## 问题 / 方法论点
+
+[填写：本轮实验要验证的关键问题，以及方法主张是什么。]
+
+## Claim 映射表
+
+| claim | 重要性 | 最低证据 | 关联实验块 |
+|---|---|---|---|
+| [填写] | [填写] | [填写] | [填写] |
+| [填写] | [填写] | [填写] | [填写] |
+| [填写] | [填写] | [填写] | [填写] |
+
+## 实验块
+
+| 实验块 | 验证 claim | 数据集 | 对比系统 | 指标 | 成功标准 | 失败解读 | 优先级 |
+|---|---|---|---|---|---|---|---|
+| [填写] | [填写] | [填写] | [填写] | [填写] | [填写] | [填写] | [填写] |
+| [填写] | [填写] | [填写] | [填写] | [填写] | [填写] | [填写] | [填写] |
+| [填写] | [填写] | [填写] | [填写] | [填写] | [填写] | [填写] | [填写] |
+
+## 运行顺序表
+
+| 里程碑 | 目标 | 运行内容 | 决策关卡 | 预估耗时 |
+|---|---|---|---|---|
+| [填写] | [填写] | [填写] | [填写] | [填写] |
+| [填写] | [填写] | [填写] | [填写] | [填写] |
+| [填写] | [填写] | [填写] | [填写] | [填写] |
+
+## 算力预算
+
+| 项目 | 预算 | 备注 |
+|---|---|---|
+| 训练 | [填写] | [填写] |
+| 评估 | [填写] | [填写] |
+| 消融 | [填写] | [填写] |
+| 总计 | [填写] | [填写] |
+
+## 风险
+
+| 风险 | 影响 | 缓解措施 |
+|---|---|---|
+| [填写] | [填写] | [填写] |
+| [填写] | [填写] | [填写] |
+| [填写] | [填写] | [填写] |
+