edit reports success for a CRLF-only line-ending change that does nothing

Describe the bug

In the edit tool, the oldString === newString guard runs on the raw input before CRLF normalization. On a CRLF file, oldString and newString that differ only in line-ending style are normalized to the same CRLF text, so the replacement becomes the identity function.

The tool then reports Replacements: 1 (success) while the file is unchanged — the model believes it applied a change (e.g. normalizing line endings) that never happened.

Steps to reproduce

CRLF file containing a\r\nb. Edit with oldString: "a\r\nb", newString: "a\nb".

Expected: either a change or a clear error. Actual: success with Replacements: 1, file unchanged.

Affected code

packages/core/src/tool/edit.ts — the identity check at the top of execute vs. the convertToLineEnding normalization further down.

Suggested fix

Re-check oldString === newString after normalization, or detect the identity replacement and return a no-op error instead of reporting success.

Environment

• opencode version: latest dev