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>

ui/src/lib/api.ts

@@ -12,6 +12,7 @@ import type {
   FeatureUpdate,
   FeatureBulkCreate,
   FeatureBulkCreateResponse,
+  DependencyGraph,
   AgentStatusResponse,
   AgentActionResponse,
   SetupStatus,
@@ -141,6 +142,50 @@ export async function createFeaturesBulk(
   })
 }
 
+// ============================================================================
+// Dependency Graph API
+// ============================================================================
+
+export async function getDependencyGraph(projectName: string): Promise<DependencyGraph> {
+  return fetchJSON(`/projects/${encodeURIComponent(projectName)}/features/graph`)
+}
+
+export async function addDependency(
+  projectName: string,
+  featureId: number,
+  dependencyId: number
+): Promise<{ success: boolean; feature_id: number; dependencies: number[] }> {
+  return fetchJSON(
+    `/projects/${encodeURIComponent(projectName)}/features/${featureId}/dependencies/${dependencyId}`,
+    { method: 'POST' }
+  )
+}
+
+export async function removeDependency(
+  projectName: string,
+  featureId: number,
+  dependencyId: number
+): Promise<{ success: boolean; feature_id: number; dependencies: number[] }> {
+  return fetchJSON(
+    `/projects/${encodeURIComponent(projectName)}/features/${featureId}/dependencies/${dependencyId}`,
+    { method: 'DELETE' }
+  )
+}
+
+export async function setDependencies(
+  projectName: string,
+  featureId: number,
+  dependencyIds: number[]
+): Promise<{ success: boolean; feature_id: number; dependencies: number[] }> {
+  return fetchJSON(
+    `/projects/${encodeURIComponent(projectName)}/features/${featureId}/dependencies`,
+    {
+      method: 'PUT',
+      body: JSON.stringify({ dependency_ids: dependencyIds }),
+    }
+  )
+}
+
 // ============================================================================
 // Agent API
 // ============================================================================
@@ -151,11 +196,19 @@ export async function getAgentStatus(projectName: string): Promise<AgentStatusRe
 
 export async function startAgent(
   projectName: string,
-  yoloMode: boolean = false
+  options: {
+    yoloMode?: boolean
+    parallelMode?: boolean
+    maxConcurrency?: number
+  } = {}
 ): Promise<AgentActionResponse> {
   return fetchJSON(`/projects/${encodeURIComponent(projectName)}/agent/start`, {
     method: 'POST',
-    body: JSON.stringify({ yolo_mode: yoloMode }),
+    body: JSON.stringify({
+      yolo_mode: options.yoloMode ?? false,
+      parallel_mode: options.parallelMode ?? false,
+      max_concurrency: options.maxConcurrency,
+    }),
   })
 }