chore: 删掉 main 上的 binDir —— 一个 shell 重定向留下的空文件

dc6eb34(#436)误提交,在 main 上待了一周。名字读起来像一个本该被展开而没有展开
的变量(`> $binDir`),内容是空的。

顺手写进 .gitignore,让同样的手滑下次被挡住而不是再被 review 一遍。

Author: speak-agent

.gitignore

@@ -43,3 +43,9 @@ bench/bench-report.json
 # --project mode writes the measured build's stdout/stderr next to the project
 bench-child.log
 .mcpp.toml.bench-backup
+
+# ⚠️ An empty file a shell redirection left behind. It was committed in #436
+# and lived on `main` for a week; the name reads like a variable that was meant
+# to be expanded (`> $binDir`) and was not. Listed so the same slip is caught
+# next time rather than reviewed again.
+binDir