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>

server/schemas.py

@@ -80,6 +80,7 @@ class FeatureBase(BaseModel):
     name: str
     description: str
     steps: list[str]
+    dependencies: list[int] = Field(default_factory=list)  # Optional dependencies
 
 
 class FeatureCreate(FeatureBase):
@@ -94,6 +95,7 @@ class FeatureUpdate(BaseModel):
     description: str | None = None
     steps: list[str] | None = None
     priority: int | None = None
+    dependencies: list[int] | None = None  # Optional - can update dependencies
 
 
 class FeatureResponse(FeatureBase):
@@ -102,6 +104,8 @@ class FeatureResponse(FeatureBase):
     priority: int
     passes: bool
     in_progress: bool
+    blocked: bool = False  # Computed: has unmet dependencies
+    blocking_dependencies: list[int] = Field(default_factory=list)  # Computed
 
     class Config:
         from_attributes = True
@@ -126,6 +130,37 @@ class FeatureBulkCreateResponse(BaseModel):
     features: list[FeatureResponse]
 
 
+# ============================================================================
+# Dependency Graph Schemas
+# ============================================================================
+
+class DependencyGraphNode(BaseModel):
+    """Minimal node for graph visualization (no description exposed for security)."""
+    id: int
+    name: str
+    category: str
+    status: Literal["pending", "in_progress", "done", "blocked"]
+    priority: int
+    dependencies: list[int]
+
+
+class DependencyGraphEdge(BaseModel):
+    """Edge in the dependency graph."""
+    source: int
+    target: int
+
+
+class DependencyGraphResponse(BaseModel):
+    """Response for dependency graph visualization."""
+    nodes: list[DependencyGraphNode]
+    edges: list[DependencyGraphEdge]
+
+
+class DependencyUpdate(BaseModel):
+    """Request schema for updating a feature's dependencies."""
+    dependency_ids: list[int] = Field(..., max_length=20)  # Security: limit
+
+
 # ============================================================================
 # Agent Schemas
 # ============================================================================
@@ -134,6 +169,8 @@ class AgentStartRequest(BaseModel):
     """Request schema for starting the agent."""
     yolo_mode: bool | None = None  # None means use global settings
     model: str | None = None  # None means use global settings
+    parallel_mode: bool | None = None  # Enable parallel execution
+    max_concurrency: int | None = None  # Max concurrent agents (1-5)
 
     @field_validator('model')
     @classmethod
@@ -143,6 +180,14 @@ class AgentStartRequest(BaseModel):
             raise ValueError(f"Invalid model. Must be one of: {VALID_MODELS}")
         return v
 
+    @field_validator('max_concurrency')
+    @classmethod
+    def validate_concurrency(cls, v: int | None) -> int | None:
+        """Validate max_concurrency is between 1 and 5."""
+        if v is not None and (v < 1 or v > 5):
+            raise ValueError("max_concurrency must be between 1 and 5")
+        return v
+
 
 class AgentStatus(BaseModel):
     """Current agent status."""
@@ -151,6 +196,8 @@ class AgentStatus(BaseModel):
     started_at: datetime | None = None
     yolo_mode: bool = False
     model: str | None = None  # Model being used by running agent
+    parallel_mode: bool = False
+    max_concurrency: int | None = None
 
 
 class AgentActionResponse(BaseModel):
@@ -180,6 +227,7 @@ class WSProgressMessage(BaseModel):
     """WebSocket message for progress updates."""
     type: Literal["progress"] = "progress"
     passing: int
+    in_progress: int
     total: int
     percentage: float
 
@@ -196,6 +244,8 @@ class WSLogMessage(BaseModel):
     type: Literal["log"] = "log"
     line: str
     timestamp: datetime
+    featureId: int | None = None
+    agentIndex: int | None = None
 
 
 class WSAgentStatusMessage(BaseModel):
@@ -204,6 +254,25 @@ class WSAgentStatusMessage(BaseModel):
     status: str
 
 
+# Agent state for multi-agent tracking
+AgentState = Literal["idle", "thinking", "working", "testing", "success", "error", "struggling"]
+
+# Agent mascot names assigned by index
+AGENT_MASCOTS = ["Spark", "Fizz", "Octo", "Hoot", "Buzz"]
+
+
+class WSAgentUpdateMessage(BaseModel):
+    """WebSocket message for multi-agent status updates."""
+    type: Literal["agent_update"] = "agent_update"
+    agentIndex: int
+    agentName: str  # One of AGENT_MASCOTS
+    featureId: int
+    featureName: str
+    state: AgentState
+    thought: str | None = None
+    timestamp: datetime
+
+
 # ============================================================================
 # Spec Chat Schemas
 # ============================================================================