feat: Add YOLO mode for rapid prototyping without browser testing

Add a new YOLO (You Only Live Once) mode that skips all browser testing
and regression tests for faster feature iteration during prototyping.

Changes made:

**Core YOLO Mode Implementation:**
- Add --yolo CLI flag to autonomous_agent_demo.py
- Update agent.py to accept yolo_mode parameter and select appropriate prompt
- Modify client.py to conditionally include Playwright MCP server (excluded in YOLO mode)
- Add coding_prompt_yolo.template.md with static analysis only verification
- Add get_coding_prompt_yolo() to prompts.py

**Server/API Updates:**
- Add AgentStartRequest schema with yolo_mode field
- Update AgentStatus to include yolo_mode
- Modify process_manager.py to pass --yolo flag to subprocess
- Update agent router to accept yolo_mode in start request

**UI Updates:**
- Add YOLO toggle button (lightning bolt icon) in AgentControl
- Show YOLO mode indicator when agent is running in YOLO mode
- Add useAgentStatus hook to track current mode
- Update startAgent API to accept yoloMode parameter
- Add YOLO toggle in SpecCreationChat completion flow

**Spec Creation Improvements:**
- Fix create-spec.md to properly replace [FEATURE_COUNT] placeholder
- Add REQUIRED FEATURE COUNT section to initializer_prompt.template.md
- Fix spec_chat_session.py to create security settings file for Claude SDK
- Delete app_spec.txt before spec creation to allow fresh creation

**Documentation:**
- Add YOLO mode section to CLAUDE.md with usage examples
- Add checkpoint.md slash command for creating detailed commits

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ui/src/App.tsx

@@ -1,5 +1,5 @@
 import { useState, useEffect, useCallback } from 'react'
-import { useProjects, useFeatures } from './hooks/useProjects'
+import { useProjects, useFeatures, useAgentStatus } from './hooks/useProjects'
 import { useProjectWebSocket } from './hooks/useWebSocket'
 import { useFeatureSound } from './hooks/useFeatureSound'
 import { useCelebration } from './hooks/useCelebration'
@@ -34,6 +34,7 @@ function App() {
 
   const { data: projects, isLoading: projectsLoading } = useProjects()
   const { data: features } = useFeatures(selectedProject)
+  const { data: agentStatusData } = useAgentStatus(selectedProject)
   const wsState = useProjectWebSocket(selectedProject)
 
   // Play sounds when features move between columns
@@ -151,6 +152,7 @@ function App() {
                   <AgentControl
                     projectName={selectedProject}
                     status={wsState.agentStatus}
+                    yoloMode={agentStatusData?.yolo_mode ?? false}
                   />
                 </>
               )}