fix(core): handle Windows paths under WSL

[emersonbusson]

Summary

• Translate Windows drive-letter paths to WSL mount paths when running under WSL.
• Preserve existing path resolution behavior for non-WSL and native Windows environments.
• Add focused coverage for WSL path translation and subpath checks.

Validation

• npm test -w @google/gemini-cli-core -- src/utils/paths.test.ts
• npm run typecheck --workspace @google/gemini-cli-core
• npm run lint --workspace @google/gemini-cli-core
• npm run build --workspace @google/gemini-cli-core
• git diff --check origin/main...HEAD

Related Issues

Related to #25527
Also related to #25184

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request improves cross-platform compatibility by enabling the CLI to correctly handle Windows-style paths when executed within a Windows Subsystem for Linux (WSL) environment. By mapping Windows drive paths to standard WSL mount points, the changes ensure that file system operations remain consistent across different operating system configurations without affecting native Windows or non-WSL environments.

Highlights

• WSL Path Translation: Introduced a utility to automatically translate Windows drive-letter paths (e.g., C:) to their corresponding WSL mount points (e.g., /mnt/c/) when running in a WSL environment.
• Environment Detection: Added robust detection for WSL environments using environment variables and kernel version checks, with caching to optimize performance.
• Integration with Path Helpers: Updated core path utility functions, including toAbsolutePath, isSubpath, and resolveToRealPath, to transparently apply WSL path translation.
• Test Coverage: Added comprehensive unit tests to verify path translation logic, WSL detection, and compatibility with existing path resolution helpers.

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[gemini-code-assist]

Code Review

This pull request introduces support for Windows Subsystem for Linux (WSL) path translation within the core utility functions. It adds logic to detect WSL environments and a translateWindowsPath function that converts Windows drive paths to their corresponding WSL mount points (e.g., /mnt/c/). This translation is now integrated into toAbsolutePath, isSubpath, and resolveToRealPath to ensure consistent path handling when running under WSL. Additionally, a new set of tests has been added to verify these changes. I have no feedback to provide.

[emersonbusson]

Rebased this PR onto current origin/main and reran the validation from the PR description.

Root cause: when the CLI runs under WSL, Windows drive-letter paths can reach the core path helpers, but Linux/Node path resolution does not translate C:\... into /mnt/c/...; that can make absolute path resolution and subpath checks fail for WSL users.

Approach: translate Windows drive-letter paths only when WSL is detected, and preserve existing behavior for non-WSL Linux/macOS and native Windows. The added tests cover WSL translation and existing subpath/path-resolution behavior.

Validation after rebase:

• npm test -w @google/gemini-cli-core -- src/utils/paths.test.ts
• npm run typecheck --workspace @google/gemini-cli-core
• npm run lint --workspace @google/gemini-cli-core
• npm run build --workspace @google/gemini-cli-core
• git diff --check origin/main...HEAD

I kept the issue references as Related to #25527 / Also related to #25184 rather than Fixes, because this PR is scoped to WSL Windows-path handling and may not fully close those broader issues. Since this PR has the 🔒 maintainer only label, could a maintainer confirm whether this external contribution is acceptable for that scope?