v1.5.0 - Git Worktree Integration

Features

• Auto-create worktree after plan approval - One worktree per plan, all issues worked in same isolated environment
• Worktree detection in /kas:next - Skips worktree creation when already in one
• Worktree cleanup in /kas:merge - Automatically removes worktree after merging

Documentation

• Simplified CLAUDE.md (-109 lines)
• Updated Git Worktree Workflow section with conventions
• Added worktree handling to commands/next.md

Conventions

• Path: .worktrees/<prefix>-<slug>/
• Branch: <prefix>/<slug>
• Prefix: feat/ (default), fix/ (for Fix:/Bug:), refactor/ (for Refactor:)