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

calculators/builder-adversary/run-05/machine-docs/JOURNAL-eval.md

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+# JOURNAL — phase: eval (Builder)
+
+## 2026-06-15 — implementation
+
+### Design
+
+AST nodes from parse phase: `Num(value)`, `BinOp(op, left, right)`, `Unary(op, operand)`.
+Evaluator is a recursive tree walk. Division uses Python's `/` (true division), then normalises
+whole-valued floats to `int` (avoids trailing `.0` in CLI output without needing special fmt logic).
+
+### Runs
+
+```
+$ python -m unittest -q
+----------------------------------------------------------------------
+Ran 56 tests in 0.002s
+
+OK
+```
+
+```
+$ python calc.py "2+3*4"
+14
+$ python calc.py "(2+3)*4"
+20
+$ python calc.py "7/2"
+3.5
+$ python calc.py "4/2"
+2
+$ python calc.py "1/0"
+error: division by zero   (stderr, exit 1)
+$ python calc.py "1 +"
+error: unexpected token 'EOF'  (stderr, exit 1)
+```
+
+### Type normalisation choice
+
+`int(result) if result == int(result) else result` — chose this over a `fmt` conversion in the CLI
+so `evaluate` itself is honest about the value type and tests can assert `isinstance(result, int)`.