Rename sandbox `excludedCommands` to `unsandboxedCommands` for clarity

Problem

excludedCommands is counterintuitive. The name suggests these commands are blocked, when they actually run outside the sandbox with no restrictions.

allowUnsandboxedCommands already uses the correct mental model in the same config block. excludedCommands should follow the same convention.

Suggestion

// Current — confusing
"excludedCommands": ["git", "docker", "brew"]

// Proposed — clear
"unsandboxedCommands": ["git", "docker", "brew"]

Keep excludedCommands as a deprecated alias for backwards compatibility.