feat: add concurrent agents with dependency system and delightful UI

Major feature implementation for parallel agent execution with dependency-aware
scheduling and an engaging multi-agent UI experience.

Backend Changes:
- Add parallel_orchestrator.py for concurrent feature processing
- Add api/dependency_resolver.py with cycle detection (Kahn's algorithm + DFS)
- Add atomic feature_claim_next() with retry limit and exponential backoff
- Fix circular dependency check arguments in 4 locations
- Add AgentTracker class for parsing agent output and emitting updates
- Add browser isolation with --isolated flag for Playwright MCP
- Extend WebSocket protocol with agent_update messages and log attribution
- Add WSAgentUpdateMessage schema with agent states and mascot names
- Fix WSProgressMessage to include in_progress field

New UI Components:
- AgentMissionControl: Dashboard showing active agents with collapsible activity
- AgentCard: Individual agent status with avatar and thought bubble
- AgentAvatar: SVG mascots (Spark, Fizz, Octo, Hoot, Buzz) with animations
- ActivityFeed: Recent activity stream with stable keys (no flickering)
- CelebrationOverlay: Confetti animation with click/Escape dismiss
- DependencyGraph: Interactive node graph visualization with dagre layout
- DependencyBadge: Visual indicator for feature dependencies
- ViewToggle: Switch between Kanban and Graph views
- KeyboardShortcutsHelp: Help overlay accessible via ? key

UI/UX Improvements:
- Celebration queue system to handle rapid success messages
- Accessibility attributes on AgentAvatar (role, aria-label, aria-live)
- Collapsible Recent Activity section with persisted preference
- Agent count display in header
- Keyboard shortcut G to toggle Kanban/Graph view
- Real-time thought bubbles and state animations

Bug Fixes:
- Fix circular dependency validation (swapped source/target arguments)
- Add MAX_CLAIM_RETRIES=10 to prevent stack overflow under contention
- Fix THOUGHT_PATTERNS to match actual [Tool: name] format
- Fix ActivityFeed key prop to prevent re-renders on new items
- Add featureId/agentIndex to log messages for proper attribution

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

.claude/templates/initializer_prompt.template.md

@@ -32,23 +32,35 @@ Use the feature_create_bulk tool to add all features at once:
 Use the feature_create_bulk tool with features=[
   {
     "category": "functional",
-    "name": "Brief feature name",
-    "description": "Brief description of the feature and what this test verifies",
+    "name": "User can create an account",
+    "description": "Basic user registration functionality",
     "steps": [
-      "Step 1: Navigate to relevant page",
-      "Step 2: Perform action",
-      "Step 3: Verify expected result"
+      "Step 1: Navigate to registration page",
+      "Step 2: Fill in required fields",
+      "Step 3: Submit form and verify account created"
     ]
   },
   {
-    "category": "style",
-    "name": "Brief feature name",
-    "description": "Brief description of UI/UX requirement",
+    "category": "functional",
+    "name": "User can log in",
+    "description": "Authentication with existing credentials",
     "steps": [
-      "Step 1: Navigate to page",
-      "Step 2: Take screenshot",
-      "Step 3: Verify visual requirements"
-    ]
+      "Step 1: Navigate to login page",
+      "Step 2: Enter credentials",
+      "Step 3: Verify successful login and redirect"
+    ],
+    "depends_on_indices": [0]
+  },
+  {
+    "category": "functional",
+    "name": "User can view dashboard",
+    "description": "Protected dashboard requires authentication",
+    "steps": [
+      "Step 1: Log in as user",
+      "Step 2: Navigate to dashboard",
+      "Step 3: Verify personalized content displays"
+    ],
+    "depends_on_indices": [1]
   }
 ]
 ```
@@ -57,6 +69,7 @@ Use the feature_create_bulk tool with features=[
 - IDs and priorities are assigned automatically based on order
 - All features start with `passes: false` by default
 - You can create features in batches if there are many (e.g., 50 at a time)
+- Use `depends_on_indices` to specify dependencies (see FEATURE DEPENDENCIES section below)
 
 **Requirements for features:**
 
@@ -75,6 +88,86 @@ Use the feature_create_bulk tool with features=[
 
 ---
 
+## FEATURE DEPENDENCIES
+
+Dependencies enable **parallel execution** of independent features. When you specify dependencies correctly, multiple agents can work on unrelated features simultaneously, dramatically speeding up development.
+
+### Why Dependencies Matter
+
+1. **Parallel Execution**: Features without dependencies can run in parallel
+2. **Logical Ordering**: Ensures features are built in the right order
+3. **Blocking Prevention**: An agent won't start a feature until its dependencies pass
+
+### How to Determine Dependencies
+
+Ask yourself: "What MUST be working before this feature can be tested?"
+
+| Dependency Type | Example |
+|-----------------|---------|
+| **Data dependencies** | "Edit item" depends on "Create item" |
+| **Auth dependencies** | "View dashboard" depends on "User can log in" |
+| **Navigation dependencies** | "Modal close works" depends on "Modal opens" |
+| **UI dependencies** | "Filter results" depends on "Display results list" |
+| **API dependencies** | "Fetch user data" depends on "API authentication" |
+
+### Using `depends_on_indices`
+
+Since feature IDs aren't assigned until after creation, use **array indices** (0-based) to reference dependencies:
+
+```json
+{
+  "features": [
+    { "name": "Create account", ... },           // Index 0
+    { "name": "Login", "depends_on_indices": [0] },  // Index 1, depends on 0
+    { "name": "View profile", "depends_on_indices": [1] }, // Index 2, depends on 1
+    { "name": "Edit profile", "depends_on_indices": [2] }  // Index 3, depends on 2
+  ]
+}
+```
+
+### Rules for Dependencies
+
+1. **Can only depend on EARLIER features**: Index must be less than current feature's position
+2. **No circular dependencies**: A cannot depend on B if B depends on A
+3. **Maximum 20 dependencies** per feature
+4. **Foundation features have NO dependencies**: First features in each category typically have none
+5. **Don't over-depend**: Only add dependencies that are truly required for testing
+
+### Best Practices
+
+1. **Start with foundation features** (index 0-10): Core setup, basic navigation, authentication
+2. **Group related features together**: Keep CRUD operations adjacent
+3. **Chain complex flows**: Registration → Login → Dashboard → Settings
+4. **Keep dependencies shallow**: Prefer 1-2 dependencies over deep chains
+5. **Skip dependencies for independent features**: Visual tests often have no dependencies
+
+### Example: Todo App Feature Chain
+
+```json
+[
+  // Foundation (no dependencies)
+  { "name": "App loads without errors", "category": "functional" },
+  { "name": "Navigation bar displays", "category": "style" },
+
+  // Auth chain
+  { "name": "User can register", "depends_on_indices": [0] },
+  { "name": "User can login", "depends_on_indices": [2] },
+  { "name": "User can logout", "depends_on_indices": [3] },
+
+  // Todo CRUD (depends on auth)
+  { "name": "User can create todo", "depends_on_indices": [3] },
+  { "name": "User can view todos", "depends_on_indices": [5] },
+  { "name": "User can edit todo", "depends_on_indices": [5] },
+  { "name": "User can delete todo", "depends_on_indices": [5] },
+
+  // Advanced features (multiple dependencies)
+  { "name": "User can filter todos", "depends_on_indices": [6] },
+  { "name": "User can search todos", "depends_on_indices": [6] }
+]
+```
+
+---
+
 ## MANDATORY TEST CATEGORIES
 
 The feature_list.json **MUST** include tests from ALL of these categories. The minimum counts scale by complexity tier.