feat: Implement CHORUS scaling improvements for robust autoscaling

Address WHOOSH issue #7 with comprehensive scaling optimizations to prevent
license server, bootstrap peer, and control plane collapse during fast scale-out.

HIGH-RISK FIXES (Must-Do):
✅ License gate already implemented with cache + circuit breaker + grace window
✅ mDNS disabled in container environments (CHORUS_MDNS_ENABLED=false)
✅ Connection rate limiting (5 dials/sec, 16 concurrent DHT queries)
✅ Connection manager with watermarks (32 low, 128 high)
✅ AutoNAT enabled for container networking

MEDIUM-RISK FIXES (Next Priority):
✅ Assignment merge layer with HTTP/file config + SIGHUP reload
✅ Runtime configuration system with WHOOSH assignment API support
✅ Election stability windows to prevent churn:
  - CHORUS_ELECTION_MIN_TERM=30s (minimum time between elections)
  - CHORUS_LEADER_MIN_TERM=45s (minimum time before challenging healthy leader)
✅ Bootstrap pool JSON support with priority sorting and join stagger

NEW FEATURES:
- Runtime config system with assignment overrides from WHOOSH
- SIGHUP reload handler for live configuration updates
- JSON bootstrap configuration with peer metadata (region, roles, priority)
- Configurable election stability windows with environment variables
- Multi-format bootstrap support: Assignment → JSON → CSV

FILES MODIFIED:
- pkg/config/assignment.go (NEW): Runtime assignment merge system
- docker/bootstrap.json (NEW): Example JSON bootstrap configuration
- pkg/election/election.go: Added stability windows and churn prevention
- internal/runtime/shared.go: Integrated assignment loading and conditional mDNS
- p2p/node.go: Added connection management and rate limiting
- pkg/config/hybrid_config.go: Added rate limiting configuration fields
- docker/docker-compose.yml: Updated environment variables and configs
- README.md: Updated status table with scaling milestone

This implementation enables wave-based autoscaling without system collapse,
addressing all scaling concerns from WHOOSH issue #7.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

internal/runtime/shared.go

@@ -105,6 +105,7 @@ func (t *SimpleTaskTracker) publishTaskCompletion(taskID string, success bool, s
 // SharedRuntime contains all the shared P2P infrastructure components
 type SharedRuntime struct {
 	Config              *config.Config
+	RuntimeConfig       *config.RuntimeConfig
 	Logger              *SimpleLogger
 	Context             context.Context
 	Cancel              context.CancelFunc
@@ -149,6 +150,28 @@ func Initialize(appMode string) (*SharedRuntime, error) {
 	runtime.Config = cfg
 
 	runtime.Logger.Info("✅ Configuration loaded successfully")
+
+	// Initialize runtime configuration with assignment support
+	runtime.RuntimeConfig = config.NewRuntimeConfig(cfg)
+
+	// Load assignment if ASSIGN_URL is configured
+	if assignURL := os.Getenv("ASSIGN_URL"); assignURL != "" {
+		runtime.Logger.Info("📡 Loading assignment from WHOOSH: %s", assignURL)
+
+		ctx, cancel := context.WithTimeout(runtime.Context, 10*time.Second)
+		if err := runtime.RuntimeConfig.LoadAssignment(ctx, assignURL); err != nil {
+			runtime.Logger.Warn("⚠️ Failed to load assignment (continuing with base config): %v", err)
+		} else {
+			runtime.Logger.Info("✅ Assignment loaded successfully")
+		}
+		cancel()
+
+		// Start reload handler for SIGHUP
+		runtime.RuntimeConfig.StartReloadHandler(runtime.Context, assignURL)
+		runtime.Logger.Info("📡 SIGHUP reload handler started for assignment updates")
+	} else {
+		runtime.Logger.Info("⚪ No ASSIGN_URL configured, using static configuration")
+	}
 	runtime.Logger.Info("🤖 Agent ID: %s", cfg.Agent.ID)
 	runtime.Logger.Info("🎯 Specialization: %s", cfg.Agent.Specialization)
 
@@ -225,12 +248,17 @@ func Initialize(appMode string) (*SharedRuntime, error) {
 	runtime.HypercoreLog = hlog
 	runtime.Logger.Info("📝 Hypercore logger initialized")
 
-	// Initialize mDNS discovery
-	mdnsDiscovery, err := discovery.NewMDNSDiscovery(ctx, node.Host(), "chorus-peer-discovery")
-	if err != nil {
-		return nil, fmt.Errorf("failed to create mDNS discovery: %v", err)
+	// Initialize mDNS discovery (disabled in container environments for scaling)
+	if cfg.V2.DHT.MDNSEnabled {
+		mdnsDiscovery, err := discovery.NewMDNSDiscovery(ctx, node.Host(), "chorus-peer-discovery")
+		if err != nil {
+			return nil, fmt.Errorf("failed to create mDNS discovery: %v", err)
+		}
+		runtime.MDNSDiscovery = mdnsDiscovery
+		runtime.Logger.Info("🔍 mDNS discovery enabled for local network")
+	} else {
+		runtime.Logger.Info("⚪ mDNS discovery disabled (recommended for container/swarm deployments)")
 	}
-	runtime.MDNSDiscovery = mdnsDiscovery
 
 	// Initialize PubSub with hypercore logging
 	ps, err := pubsub.NewPubSubWithLogger(ctx, node.Host(), "chorus/coordination/v1", "hmmm/meta-discussion/v1", hlog)
@@ -283,6 +311,7 @@ func (r *SharedRuntime) Cleanup() {
 
 	if r.MDNSDiscovery != nil {
 		r.MDNSDiscovery.Close()
+		r.Logger.Info("🔍 mDNS discovery closed")
 	}
 
 	if r.PubSub != nil {
@@ -407,8 +436,20 @@ func (r *SharedRuntime) initializeDHTStorage() error {
 				}
 			}
 
-			// Connect to bootstrap peers if configured
-			for _, addrStr := range r.Config.V2.DHT.BootstrapPeers {
+			// Connect to bootstrap peers (with assignment override support)
+			bootstrapPeers := r.RuntimeConfig.GetBootstrapPeers()
+			if len(bootstrapPeers) == 0 {
+				bootstrapPeers = r.Config.V2.DHT.BootstrapPeers
+			}
+
+			// Apply join stagger if configured
+			joinStagger := r.RuntimeConfig.GetJoinStagger()
+			if joinStagger > 0 {
+				r.Logger.Info("⏱️ Applying join stagger delay: %v", joinStagger)
+				time.Sleep(joinStagger)
+			}
+
+			for _, addrStr := range bootstrapPeers {
 				addr, err := multiaddr.NewMultiaddr(addrStr)
 				if err != nil {
 					r.Logger.Warn("⚠️ Invalid bootstrap address %s: %v", addrStr, err)