add CLAUDE.md

Author: thiagowfx

CLAUDE.md

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+- Follow @op_login_all/ as a canonical style / pattern for shell scripts.
+    - In general, follow the Google Shell style guide.
+    - Ensure shellcheck passes (via pre-commit).
+    - Use a "main" function.
+    - Every script must support -h / --help for usage instructions.
+    - In particular, always include a user-friendly README.md.
+    - *DO NOT* use ALL CAPS. Exception: headers. For example: "OPTIONS:".
+    - Avoid "please". Be direct and succinct.
+    - Always test the script works as expected. Write unit tests whenever it
+      makes sense to do so.
+    - Use clever / funny placeholders when illustrating ID / input examples.