- Add bubbletea/lipgloss/glamour dependencies for TUI
- Create internal/tui package with EventWriter, styles, and bubbletea Model
- Support streaming output display in conversation window
- Add right panel with statistics and active agent status
- Implement multi-agent collaboration with sub-agents
- Add AgentCallTool for delegating tasks to sub-agents
- Support parallel tool execution with goroutines
- Auto-discover sub-agents from ~/.orca/prompts/ directory
- Fix orchestrator routing based on msg.To field
- Add non-blocking event writer with timeout to prevent blocking
