[FEATURE] Preserve SlashCommand permission rules when using Skill tool

Problem

When users define permission rules like SlashCommand(/foo:*) in their settings.json#permissions#allow, those permissions are no longer respected. This is because slash commands are now invoked via the Skill tool internally, but the permission system still checks against SlashCommand which is no longer used.

This is a breaking change for users who have configured their permissions around the SlashCommand tool name.

Proposed solution

Until v3 release, maintain backwards compatibility by:

1. Continuing to honor SlashCommand permission patterns in settings.json#permissions#allow
2. Mapping Skill tool calls for slash commands to check both Skill and SlashCommand permissions
3. Only fully deprecate SlashCommand permissions in a major version bump (v3) where breaking changes are expected

Alternatives considered

• Users could manually update all their permission rules from SlashCommand(/foo:*) to the new Skill equivalent, but this is disruptive and unexpected for a minor/patch release

Priority

High - This is a breaking change affecting existing user configurations

Category

Configuration and settings