[bennycode]

Fixes #125

module.exports = <expr> only produced an ESM export when the value was an identifier or a function expression. For anything else the statement was removed without a replacement, so exports disappeared silently.

• Object literals that only reference identifiers become named exports: module.exports = { c0, one: c1 } becomes export { c0, c1 as one };
• Every other expression (object literals with values, arrow functions, classes, require calls) becomes export default <expr>, so no code is dropped.

While fixing this I found a related bug in the module.exports.foo = … path, which always emitted export { <right side> }:

• module.exports.foo = bar exported bar instead of foo. It now emits export { bar as foo }.
• Non-identifier values produced invalid code like export { 42 }. They now emit export const answer = 42;
• When the name is a reserved word (class, default, …) or already used in the file, the value goes through a local alias: const _answer = …; export { _answer as answer };
• Deeper paths like module.exports.a.b = 1 used to be flattened into export { 1 }. They are now left untouched.

The "already used" check is conservative. It treats any identifier with the same text in the file as taken, so some exports get an alias they don't strictly need. The output is valid either way.

Supersedes #166, which only handled identifier-only object literals.