feat: add /spec mode for structured development workflow

[lroolle]

Description

Add /spec mode functionality to claude-yolo for structured development workflow inspired by kiro.dev.

Type

• Bug fix
• New feature
• Enhancement
• Documentation

Details

Implement a structured development workflow that transforms user prompts into organized specifications with three phases:

1. Requirements generation (user stories with EARS notation)
2. Design documentation (technical architecture, diagrams, interfaces)
3. Task breakdown (discrete, trackable implementation tasks)

Core Features:

• Generate structured specs in .claude-specs/ directory
• Create requirements.md, design.md, and tasks.md files
• Support iterative refinement of specifications
• Context-aware analysis of existing codebase
• Task execution with progress tracking

Command Interface:

claude.sh --spec "Add user authentication system"
claude.sh --spec-file my-spec.txt
claude.sh --spec-interactive
claude.sh --spec-execute spec-name

Directory Structure:

project/
├── .claude-specs/
│   ├── auth-system/
│   │   ├── requirements.md
│   │   ├── design.md
│   │   └── tasks.md

Related Files

• claude.sh (command parser and spec mode logic)
• docker-entrypoint.sh (Docker integration)
• README.md (documentation)
• New: spec-mode handlers and templates

Test Plan

• Test spec generation from simple prompts
• Verify structured file output (requirements.md, design.md, tasks.md)
• Test interactive spec refinement
• Validate task execution workflow
• Test Docker/YOLO mode integration
• Ensure proper file permissions and directory structure
• Test with various project types and sizes
• Update documentation with examples

Inspired by: kiro.dev spec mode functionality

[lroolle]

Update: Leverage Sub-Agents Feature

After reviewing Claude Code 1.0.60's new custom sub-agents feature, we should implement /spec mode as a specialized sub-agent rather than a separate command mode.

Why Sub-Agent Approach is Better:

• Clean context: Spec generation gets its own context window, keeping main conversation focused
• Reusable: Once created, the spec sub-agent works across all projects
• Tool-specific: Can be configured with only the tools needed for spec generation
• Team sharing: Project-level sub-agents can be version controlled and shared

Proposed Implementation:
Create a spec-generator sub-agent in .claude/agents/spec-generator.md:

---
name: spec-generator  
description: Structured development workflow specialist. Use for breaking down features into requirements, design, and tasks. Creates organized specs in .claude-specs/ directory.
tools: Read, Write, Grep, Glob, LS
---

You are a spec generation expert specializing in structured development workflows.

When invoked:
1. Analyze user prompt and existing codebase
2. Generate requirements.md (user stories with EARS notation)
3. Create design.md (technical architecture, interfaces) 
4. Break down into tasks.md (discrete, trackable items)
5. Save structured output to .claude-specs/{feature-name}/

[Detailed system prompt for 3-phase workflow...]

User Experience:

# Automatic delegation
claude.sh "Add user authentication system" 
# → Claude detects spec work, delegates to spec-generator sub-agent

# Explicit invocation  
claude.sh "Use the spec-generator to plan OAuth integration"

This approach integrates naturally with existing Claude Code workflows while providing the structured spec generation we need.