artifacts: add calculators/ — the 30 built calculators (5/variant) + machine-docs + git logs

calculators/builder-adversary-lean/run-03/machine-docs/BACKLOG-eval.md

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+# BACKLOG — phase eval
+
+_Builder owns "## Build backlog". Adversary owns "## Adversary findings"._
+
+## Build backlog
+
+- [x] D1: arithmetic evaluation (evaluate + test)
+- [x] D2: true division + EvalError for div-by-zero
+- [x] D3: result type coercion (int vs float)
+- [x] D4: CLI (calc.py)
+- [x] D5: full test suite green (68 tests)
+- [ ] Adversary PASS on D1
+- [ ] Adversary PASS on D2
+- [ ] Adversary PASS on D3
+- [ ] Adversary PASS on D4
+- [ ] Adversary PASS on D5
+- [ ] Write ## DONE to STATUS-eval.md
+
+## Adversary findings
+
+_(none yet — phase not started)_