feat: add tmp/ directory for temp files and cookie, add .gitignore

- tmp/ 用于存放临时文件（文档缓存、cookie等），已加入 .gitignore
- 文档中所有临时文件和 cookie 路径统一指向 tmp/
- SKILL.md 架构图增加 tmp/ 说明

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sources/tencent-doc/v1/usage.md

@@ -42,12 +42,12 @@ mcporter call tencent-docs smartcanvas.read file_id=<FILE_ID> size=10
 
 ```bash
 # 获取完整文档结构
-mcporter call tencent-docs doc.resolve_document_structure file_id=<FILE_ID> > doc_raw.json
+mcporter call tencent-docs doc.resolve_document_structure file_id=<FILE_ID> > tmp/doc_raw.json
 
 # 提取纯文本
 python -X utf8 -c "
 import json
-with open('doc_raw.json','r',encoding='utf-8') as f:
+with open('tmp/doc_raw.json','r',encoding='utf-8') as f:
     data=json.load(f)
 texts=[]
 for n in data.get('nodes',[]):
@@ -55,13 +55,13 @@ for n in data.get('nodes',[]):
     hl=n.get('heading_level',0)
     if p:
         texts.append(('#'*hl+' '+p) if hl>0 else p)
-with open('doc_content.txt','w',encoding='utf-8') as f:
+with open('tmp/doc_content.txt','w',encoding='utf-8') as f:
     f.write('\n'.join(texts))
 print(f'Done: {len(texts)} paragraphs')
 "
 
 # 清理中间文件
-rm doc_raw.json
+rm tmp/doc_raw.json
 ```
 
 ### 第二步 B：smartcanvas 类型（支持分页）