apply_patch forces a trailing newline onto files that lacked one

Describe the bug

packages/core/src/patch.ts derive() unconditionally appends a trailing newline to the result: if (updated.at(-1) !== "") updated.push("").

So apply_patch on a file that lacks a trailing newline adds one even when the patch doesn't touch the last line. patchFile then diffs before (no trailing newline) against after (with one), reporting a change the model never requested.

Repro: derive("f", [{ oldLines: ["line1"], newLines: ["LINE1"] }], "line1\nline2\nline3") → "LINE1\nline2\nline3\n".

Question

Is the forced trailing newline intentional (normalize EOF newline), or should the result preserve whether the original file ended with a newline?

Environment

• opencode version: latest dev