[superWorldSavior]

Summary

• The bug. exprToString only parenthesised an operand that binds more loosely than its parent.
  • A right operand at the same level as - or / lost its parentheses: thrust / (totalMass * 9.81) ≥ 2 was shown as thrust / totalMass * 9.81 ≥ 2.
  • That is a different expression from the one evaluated. The computed value was right; the text was wrong.
  • Seen in mcp-syson's validation viewer, while checking fix(constraint): read decimal literals in constraint expressions mcp-syson#10.
• The fix. Operands are now parenthesised by side and operator:
  • the right operand of - or / at the same level: a - (b - c), a / (b * c);
  • a comparison inside a comparison;
  • a negation on the right: a - (-b);
  • a unary minus over a compound or negated operand: -(a + b), -(-a).
• Unchanged. Parentheses that change nothing are still left out: a - b - c, a * b * c, a + b - c, (a + b) * 2, t ≥ -10 and t ≤ 80.

Test plan

• New tests/format_test.ts (the first tests for format.ts). Three of its four tests failed before the fix. The fourth pins the cases that must stay free of parentheses.
• deno task test (35 passed, z3 included), deno task check, deno lint, and deno fmt --check on the changed files.
  • Nine files on main are already unformatted; this PR leaves them alone.

Not done here

• No version bump and no JSR publication.
• mcp-syson will pick the fix up once a version is published and its deno.json moves off jsr:@casys/constraint-solver@0.1.0.

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