fix(core): add /nix/store to trusted system paths for Nix package manager

[Dakshx07]

Problem

On systems using the Nix package manager (NixOS, nix-darwin, devenv), binaries like rg (Ripgrep) are resolved to paths under /nix/store/.... However, isTrustedSystemPath() uses a hardcoded allowlist that does not include /nix/store.

This caused:

1. rg to be rejected as untrusted
2. Fallback to GrepTool (standard grep)
3. Standard grep ignoring .gitignore, causing indefinite hangs on large projects with target/, node_modules/, etc.

Fixes #28251

Changes

• packages/core/src/utils/paths.ts: Added /nix/store to trustedPrefixes in isTrustedSystemPath(), consistent with how Homebrew (/opt/homebrew, /usr/local/Cellar) is already handled.
• packages/core/src/utils/paths.test.ts: Added tests verifying /nix/store/... paths are trusted on both linux (NixOS) and darwin (nix-darwin).

Testing

All 118 existing tests pass + 3 new Nix-specific test cases added.

[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 addresses an issue where binaries managed by the Nix package manager were not recognized as trusted system paths. By updating the allowlist in the core utilities, the system can now correctly identify and utilize these binaries, preventing performance degradation caused by falling back to less efficient tools.

Highlights

• Nix Store Support: Added '/nix/store' to the trusted system path allowlist to support binaries managed by the Nix package manager.
• Improved Tool Reliability: Ensures that tools like Ripgrep are correctly identified as trusted, preventing unnecessary fallbacks to standard grep that caused performance issues.
• Enhanced Test Coverage: Added new unit tests to verify that Nix store paths are correctly validated on both Linux and macOS platforms.

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[github-actions]

📊 PR Size: size/S

• Lines changed: 26
• Additions: +26
• Deletions: -0
• Files changed: 2

[google-cla]

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View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[gemini-code-assist]

Code Review

This pull request adds /nix/store to the list of trusted system paths on macOS and Linux in packages/core/src/utils/paths.ts, and introduces corresponding unit tests in packages/core/src/utils/paths.test.ts. There are no review comments, and I have no feedback to provide.

[gemini-cli]

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This PR will be closed in 7 days if it remains without that designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding.

[gemini-cli]

This pull request is being closed as it has been open for 14 days without a 'help wanted' designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding.