Configure esbuild to transpile optional chaining

Editor assessment

The subject `fix: configure esbuild to transpile optional chaining` states the mechanism and the exact compatibility problem — optional chaining syntax unsupported downstream — completely. The fix type fits a syntax-compatibility correction, and the esbuild naming substitutes for a scope. The `fix #565` footer is well-formed and links the report. No body is present, acceptable because subject plus reference fully frame the change. No junk. Specific and traceable.