Fix REPL executor illegal return parse issue

[epi13]

Motivation

• Bundlers or tooling that strip top-level export declarations could remove export function createReplExecutor(...) and leave a stray top-level return, producing Uncaught SyntaxError: Illegal return statement at runtime.
• The change ensures the executor function remains present even if export lines are removed by a build step.

Description

• Replaced export function createReplExecutor(...) with a regular function createReplExecutor(...) declaration in src/REPLCalc/assets/js/repl-executor.js.
• Added an explicit named export export { createReplExecutor }; and kept the existing alias export const createExecutor = createReplExecutor; so imports remain compatible.
• The change is limited to the single file src/REPLCalc/assets/js/repl-executor.js and preserves existing API shape.

Testing

• Ran node --check src/REPLCalc/assets/js/repl-executor.js which completed successfully.
• Ran node --check src/REPLCalc/assets/js/repl-core.js which completed successfully.

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Codex Task