Bug: list-directory path traversal — missing path.sep in startsWith check

[dsurchisactive]

Description

The path traversal check in listDirectory() can be bypassed using sibling directory names that share a prefix with the project path.

Root Cause

In sdk/src/tools/list-directory.ts (line 16):

const resolvedPath = path.resolve(projectPath, directoryPath)
if (!resolvedPath.startsWith(projectPath)) { ... }

If projectPath is /home/user/project and directoryPath is ../project-evil, the resolved path /home/user/project-evil passes the startsWith('/home/user/project') check because it's a string prefix match.

The same codebase gets this right in code-search.ts (lines 52-53):

if (
  !searchCwd.startsWith(projectRoot + path.sep) &&
  searchCwd !== projectRoot
) { ... }

Impact

A sandboxed agent or user-controlled directoryPath parameter can list directories outside the declared project root, as long as the sibling directory name starts with the project directory name.

Suggested Fix

if (
  !resolvedPath.startsWith(projectPath + path.sep) &&
  resolvedPath !== projectPath
) {
  return [{ type: 'json', value: { errorMessage: `Invalid path...` } }]
}

This matches the pattern already used in code-search.ts.