Initialize harness coding docs from design spec

Split docs/softbox-catalog-design.md into the numbered harness doc set
(00-06, api.md, current-state, agent-context, tasks) following the
harness_coding_docs template and soft_quay conventions. Register the
nine open decision items from the design spec into the 06-tasks
roadmap as W- tasks and backlog entries. Keep the original design
spec as an archived design input with a header note.

Recreated after the repository's previous git history was lost to an
external reset; content matches the original initial commit.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

progress.md

@@ -0,0 +1,6 @@
+# 项目大事记(可选历史归档)
+
+> 执行记录默认写进各任务文件(`docs/tasks/W-<编号>.md`)的 `## 执行记录`;本文只记项目级大事,不逐任务追加。
+
+- 2026-07-19:完成设计规格 `docs/softbox-catalog-design.md` 初稿。
+- 2026-07-20:按 harness coding 模板建立文档集(00~06、api、tasks、agent-context 等),设计规格拆分归位;仓库初始化 git。