chore(docs): remove obsolete documentation files

Remove documentation files that referenced the old TypeScript/Next.js/pnpm
architecture. The project has been simplified to a Go-only collector.

Removed:
- docs/api/ - REST API docs for old web backend
- docs/design/ - React UI design system
- docs/dev/ - Old specs structure docs with pnpm commands
- docs/guides/ - NPM, Vercel, TypeScript validation guides
- docs/project/ - AI-native project management (TypeScript-based)

Kept:
- docs/reference/ - Core AI agent memory challenge documents (still relevant)

Author: Marvin Zhang

docs/README.md

@@ -1,6 +1,6 @@
 # Documentation
 
-This directory contains detailed documentation for the devlog project.
+This directory contains reference documentation for the devlog project.
 
 ## 🎯 Project Purpose & Context
 
@@ -11,14 +11,16 @@ These documents explain the fundamental challenges this project addresses: how A
 ## 📁 Directory Structure
 
 ### `/reference/` - Core Reference Documents
-- **[Detailed Analysis of Memory Loss Risks in Agentic/Autonomous AI Coding Applications for Large Tasks](reference/ai-agent-memory-challenge.md)** - Comprehensive analysis of memory loss risks in autonomous AI coding applications for large tasks
-- **[大型任务中代理/自主AI编程应用内存丢失风险的详细分析](reference/ai-agent-memory-challenge-zh.md)** - Chinese version of the memory challenge analysis
-- **[Devlog Status Workflow Guide](reference/devlog-status-workflow.md)** - Complete guide to devlog status system and workflow best practices
+
+- **[AI Agent Memory Challenge](reference/ai-agent-memory-challenge.md)** - Comprehensive analysis of memory loss risks in autonomous AI coding applications for large tasks
+- **[AI Agent Memory Challenge (中文)](reference/ai-agent-memory-challenge-zh.md)** - Chinese version of the memory challenge analysis
 
 ## 🚀 Quick Start
 
 ### 🎯 For New Users - Start Here!
+
 **READ FIRST**: The [**AI Agent Memory Challenge**](reference/ai-agent-memory-challenge.md) document is essential reading. It explains:
+
 - Why AI assistants lose context on large projects
 - The specific problems devlog solves
 - How persistent logging maintains development coherence