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

calculators/builder-adversary/run-05/machine-docs/DECISIONS.md

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+# DECISIONS — shared (append-only)
+
+## 2026-06-15 — Token.value for non-numeric tokens
+
+Decision: `Token.value` is `None` for operator/paren/EOF tokens, and `int` or `float` for NUMBER tokens.
+Rationale: Parser phases only need the numeric value; operator/paren tokens carry no useful payload beyond their kind.
+
+## 2026-06-15 — Float parsing strategy
+
+Decision: Use Python's built-in `float()` for converting float literals. Detect float vs int by presence of `.` in the matched string.
+Rationale: Handles edge cases like `.5` and `10.` correctly via stdlib, avoids manual parsing bugs.