chore: clean redundant docs, scripts, and tracked artifacts

Remove outdated plans, duplicate guides, unused tool prototypes, and
broken examples. Stop tracking generated results samples and whitelist
only the projects template and bundled KB in gitignore.

Author: bx33661

.gitignore

@@ -46,7 +46,7 @@ config\\keys*.toml
 
 *.log
 
-# 临时文件
+# 临时与生成物
 temp/
 tmp/
 *.tmp
@@ -55,12 +55,17 @@ tmp/
 output/
 results/
 
+# 案例工作区：默认忽略，仅跟踪模板与内置 KB
+projects/*
+!projects/README.md
+!projects/case-template/
+!projects/case-template/**
+!projects/python_kb/
+!projects/python_kb/**
+
 # OS
-projects/
 .DS_Store
 Thumbs.db
 .projects/
 *.zip
-projects/*.zip
-projects/C_Qi
 utils/lsp