feat(shell): add .zshenv Homebrew init and Trash-backed rm

Move brew shellenv into .zshenv so PATH is available outside
interactive shells, and make install guarantee a Trash backend
for safer rm aliases on both macOS and Linux.

.zshenv

@@ -0,0 +1,5 @@
+if [ -x /opt/homebrew/bin/brew ]; then
+    eval "$(/opt/homebrew/bin/brew shellenv)"
+elif [ -x /usr/local/bin/brew ]; then
+    eval "$(/usr/local/bin/brew shellenv)"
+fi