chore: seed sandbox project

CLAUDE.md

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+# typosaurus-sandbox
+
+A minimal Python calculator used to verify the Typosaurus agent system.
+
+## Conventions
+- Every source file starts with the `# retoor <retoor@molodetz.nl>` header.
+- Full type annotations on every function signature.
+- No comments or docstrings in source files.
+
+## Verification
+
+```
+make verify
+```

Makefile

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+verify:
+	@python3 -m compileall -q src && echo "verification passed"

src/calculator.py

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+# retoor <retoor@molodetz.nl>
+
+def add(left: int, right: int) -> int:
+    return left + right
+
+
+def subtract(left: int, right: int) -> int:
+    return left - right