Suboptimal treeshaking on pure function calls

It doesn't seem like esbuild is removing these pure function calls

```js
import { html, clone, first_child, append, define } from "@intrnl/velvet/internal";
let template0 = /*#__PURE__*/ html("

function setup($$root, $$host) {
let fragment0 = /*#__PURE__*/ clone(template0);

// these are deliberately commented out, though they are relevant
// let child0 = /*#__PURE__*/ first_child(fragment0);
// let child1 = /*#__PURE__*/ first_child(child0);
// append($$root, fragment0);
}

export default define("x-app", setup, {}, []);
```

Does it matter if the REPL has said import externalized?

[REPL link](https://esbuild.github.io/try/#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)

Start with the linked esbuild REPL reproduction and inspect the generated output for entry.js, comparing the behavior of the annotated pure calls with the commented-out calls. Determine whether the externalized import affects tree shaking; done means the reproducible pure calls are removed when their results are unused.

Written by the indexing model from the issue text.