feat: add dedicated testing agents and enhanced parallel orchestration

Introduce a new testing agent architecture that runs regression tests
independently from coding agents, improving quality assurance in
parallel mode.

Key changes:

Testing Agent System:
- Add testing_prompt.template.md for dedicated testing agent role
- Add feature_mark_failing MCP tool for regression detection
- Add --agent-type flag to select initializer/coding/testing mode
- Remove regression testing from coding prompt (now handled by testing agents)

Parallel Orchestrator Enhancements:
- Add testing agent spawning with configurable ratio (--testing-agent-ratio)
- Add comprehensive debug logging system (DebugLog class)
- Improve database session management to prevent stale reads
- Add engine.dispose() calls to refresh connections after subprocess commits
- Fix f-string linting issues (remove unnecessary f-prefixes)

UI Improvements:
- Add testing agent mascot (Chip) to AgentAvatar
- Enhance AgentCard to display testing agent status
- Add testing agent ratio slider in SettingsModal
- Update WebSocket handling for testing agent updates
- Improve ActivityFeed to show testing agent activity

API & Server Updates:
- Add testing_agent_ratio to settings schema and endpoints
- Update process manager to support testing agent type
- Enhance WebSocket messages for agent_update events

Template Changes:
- Delete coding_prompt_yolo.template.md (consolidated into main prompt)
- Update initializer_prompt.template.md with improved structure
- Streamline coding_prompt.template.md workflow

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

ui/src/components/AgentControl.tsx

@@ -24,21 +24,24 @@ export function AgentControl({ projectName, status }: AgentControlProps) {
 
   const isLoading = startAgent.isPending || stopAgent.isPending
   const isRunning = status === 'running' || status === 'paused'
+  const isLoadingStatus = status === 'loading'  // Status unknown, waiting for WebSocket
   const isParallel = concurrency > 1
 
   const handleStart = () => startAgent.mutate({
     yoloMode,
     parallelMode: isParallel,
-    maxConcurrency: isParallel ? concurrency : undefined,
+    maxConcurrency: concurrency,  // Always pass concurrency (1-5)
+    testingAgentRatio: settings?.testing_agent_ratio,
+    countTestingInConcurrency: settings?.count_testing_in_concurrency,
   })
   const handleStop = () => stopAgent.mutate()
 
-  // Simplified: either show Start (when stopped/crashed) or Stop (when running/paused)
+  // Simplified: either show Start (when stopped/crashed), Stop (when running/paused), or loading spinner
   const isStopped = status === 'stopped' || status === 'crashed'
 
   return (
     <div className="flex items-center gap-2">
-      {/* Concurrency slider - always visible when stopped */}
+      {/* Concurrency slider - visible when stopped (not during loading or running) */}
       {isStopped && (
         <div className="flex items-center gap-2">
           <GitBranch size={16} className={isParallel ? 'text-[var(--color-neo-primary)]' : 'text-gray-400'} />
@@ -67,7 +70,16 @@ export function AgentControl({ projectName, status }: AgentControlProps) {
         </div>
       )}
 
-      {isStopped ? (
+      {isLoadingStatus ? (
+        <button
+          disabled
+          className="neo-btn text-sm py-2 px-3 opacity-50 cursor-not-allowed"
+          title="Loading agent status..."
+          aria-label="Loading agent status"
+        >
+          <Loader2 size={18} className="animate-spin" />
+        </button>
+      ) : isStopped ? (
         <button
           onClick={handleStart}
           disabled={isLoading}