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>

prompts.py

@@ -74,31 +74,30 @@ def get_coding_prompt(project_dir: Path | None = None) -> str:
     return load_prompt("coding_prompt", project_dir)
 
 
-def get_coding_prompt_yolo(project_dir: Path | None = None) -> str:
-    """Load the YOLO mode coding agent prompt (project-specific if available)."""
-    return load_prompt("coding_prompt_yolo", project_dir)
+def get_testing_prompt(project_dir: Path | None = None) -> str:
+    """Load the testing agent prompt (project-specific if available)."""
+    return load_prompt("testing_prompt", project_dir)
 
 
 def get_single_feature_prompt(feature_id: int, project_dir: Path | None = None, yolo_mode: bool = False) -> str:
     """
     Load the coding prompt with single-feature focus instructions prepended.
 
-    When the parallel orchestrator assigns a specific feature to an agent,
+    When the orchestrator assigns a specific feature to a coding agent,
     this prompt ensures the agent works ONLY on that feature.
 
     Args:
         feature_id: The specific feature ID to work on
         project_dir: Optional project directory for project-specific prompts
-        yolo_mode: If True, use the YOLO prompt variant
+        yolo_mode: Ignored (kept for backward compatibility). Testing is now
+                   handled by separate testing agents, not YOLO prompts.
 
     Returns:
         The prompt with single-feature instructions prepended
     """
-    # Get the base prompt
-    if yolo_mode:
-        base_prompt = get_coding_prompt_yolo(project_dir)
-    else:
-        base_prompt = get_coding_prompt(project_dir)
+    # Always use the standard coding prompt
+    # (Testing/regression is handled by separate testing agents)
+    base_prompt = get_coding_prompt(project_dir)
 
     # Prepend single-feature instructions
     single_feature_header = f"""## SINGLE FEATURE MODE
@@ -185,8 +184,8 @@ def scaffold_project_prompts(project_dir: Path) -> Path:
     templates = [
         ("app_spec.template.txt", "app_spec.txt"),
         ("coding_prompt.template.md", "coding_prompt.md"),
-        ("coding_prompt_yolo.template.md", "coding_prompt_yolo.md"),
         ("initializer_prompt.template.md", "initializer_prompt.md"),
+        ("testing_prompt.template.md", "testing_prompt.md"),
     ]
 
     copied_files = []