feat: add interactive tool playground with AI-powered execution
Implement comprehensive tool testing environment with real package execution, AI agents, and token tracking.
**New Features:**
- Interactive playground UI with 4 tabs (Input, Output, Logs, Token Usage)
- Real npm package execution in VM2 sandbox with security constraints
- AI-powered tool execution using AI SDK v5 and GPT-4 Turbo
- Server-Sent Events (SSE) streaming for real-time progress updates
- Comprehensive 4-category token tracking (Input, Tool Description, Schema, Output)
- Visual token breakdown with colored progress bars
- IP-based rate limiting (10 executions/hour per IP)
- Database persistence of all simulations with full metadata
**Database Schema:**
- New `Simulation` model for execution records
- New `TokenUsage` model for detailed token metrics
- New `ExecutionLog` model for execution event tracking
- Added simulations relation to Tool model
**Package Executor (@tpmjs/package-executor):**
- VM2 sandbox with 5-second timeout
- Blocked dangerous modules (fs, net, http, https, child_process)
- LRU file system cache in /tmp/.tpmjs-cache
- Package installation and caching strategy
**AI Agent Service:**
- TPMJS parameter to Zod schema conversion
- AI SDK tool definition generation
- Token counting using tiktoken library
- GPT-4 Turbo pricing estimation
- Streaming text execution with callbacks
**API Endpoints:**
- POST /api/tools/[...slug]/execute - SSE streaming execution
- GET /api/tools/[...slug]/simulations - Execution history
- Rate limit headers (X-RateLimit-Limit, X-RateLimit-Remaining)
**Frontend Components:**
- ToolPlayground - Main playground UI with tabs
- TokenBreakdown - Visual token metrics with colored bars
- Integrated above README section on tool detail pages
**Security:**
- VM2 sandboxing prevents filesystem/network access
- Rate limiting prevents abuse
- IP tracking for usage monitoring
- Timeout protection (60s max API duration, 5s VM timeout)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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