CommonJS model: comma expressions are not a familiar shape, so minified files always fall back #38

Found in the round-1 review of branch fix/commonjs-model-gaps (stacked on PR #29, which fixes #34).

familiar() has no rule for a comma expression. Minified output joins top-level writes with commas, so it always fails the gate. That limits the !0 marker fix (#34) to its 'ES module interop default' path.

Repro: "use strict";Object.defineProperty(exports,"__esModule",{value:!0}),exports.load=void 0;function load(){return 1}exports.load=load; gives unfamiliar top-level ExpressionStatement.

Fix direction: treat a comma expression as familiar when every operand is a familiar expression statement.