fix(shell): avoid non-string stdout parsing in cygpath path resolution

[SpencerJung]

Issue for this PR

Closes #26932

What does this PR do?

This replaces the spawner.lines(...) call inside packages/opencode/src/tool/shell.ts's Windows cygpath() helper with an explicit spawn() + stdout decode flow.

That keeps stdout as a guaranteed string before calling .split(), and only parses the first line when the subprocess exits successfully. If the helper fails, behavior stays the same and path resolution falls back cleanly.

Why this fixes the issue

The reported crash happens before the shell subprocess actually runs because the output handling path assumes stdout is already a string. By collecting and decoding handle.stdout ourselves, this code no longer depends on that brittle path and avoids the (result.stdout ?? "").split is not a function failure.

Verification

• lsp_diagnostics on packages/opencode/src/tool/shell.ts: no diagnostics
• bun test test/tool/shell.test.ts in packages/opencode: failed due missing dependency module @babel/helper-validator-identifier after install problems
• bun x tsc -p tsconfig.json --noEmit in packages/opencode: failed due existing/missing dependency type resolution errors (for example solid-js, drizzle-orm, zod)
• bun install at repo root: failed because tree-sitter-powershell native build could not find a Visual Studio C++ toolchain on this Windows machine

Scope

• Single-file fix only: packages/opencode/src/tool/shell.ts
• No lockfiles modified

[github-actions]

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential duplicate found:

• PR fix(shell): avoid non-string stdout parsing in cygpath path resolution #28075: fix(shell): avoid non-string stdout parsing in cygpath path resolution
  • fix(shell): avoid non-string stdout parsing in cygpath path resolution #28075

Why it's related: This PR has the identical title and appears to address the same issue with cygpath stdout parsing in the Windows shell path resolution. It's likely an earlier attempt or related fix for the same problem that issue #26932 describes.

[github-actions]

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