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>

.gitignore

@@ -0,0 +1,15 @@
+# 构建产物
+/dist/
+/bin/
+
+# 本机私有配置(示例文件用 *.example 入库)
+*.env
+!*.env.example
+
+# 密钥材料绝不入库(测试密钥对放 testdata/ 并显式命名)
+*.pem
+*.key
+
+# 工具缓存
+__pycache__/
+*.pyc