[BUG] Write tool produces LF-only line endings on Windows, breaking batch (.bat) files #31224

Description

The write tool produces LF-only (\n) line endings on Windows when writing .bat/.cmd files. Cmd.exe requires CRLF (\r\n) line endings; LF-only causes the batch file to exit immediately with no visible error.

Root Cause

packages/opencode/src/tool/write.ts passes content directly to writeWithDirs() 鈫?writeFileString() in packages/core/src/fs-util.ts with no line ending conversion. Contrast with edit.ts:46-56 which already has detectLineEnding()/convertToLineEnding() helpers.

Expected Behavior

• Windows .bat/.cmd files: CRLF line endings, UTF-8 without BOM
• Other files: no transformation needed

Suggested Fix

In write.ts, detect .bat/.cmd extensions on process.platform === 'win32' and normalize line endings to CRLF before writing. For encoding, write UTF-8 without BOM (BOM before @echo off causes cmd.exe to crash on some Windows configurations).

See also the companion discussion in #31275 (closed as out-of-scope 鈥?AGENTS.md rules are user/AI-authored, not program-bundled).