docs: Add Phase 3 coordination and infrastructure documentation

Comprehensive documentation for coordination, messaging, discovery, and internal systems.

Core Coordination Packages:
- pkg/election - Democratic leader election (uptime-based, heartbeat mechanism, SLURP integration)
- pkg/coordination - Meta-coordination with dependency detection (4 built-in rules)
- coordinator/ - Task orchestration and assignment (AI-powered scoring)
- discovery/ - mDNS peer discovery (automatic LAN detection)

Messaging & P2P Infrastructure:
- pubsub/ - GossipSub messaging (31 message types, role-based topics, HMMM integration)
- p2p/ - libp2p networking (DHT modes, connection management, security)

Monitoring & Health:
- pkg/metrics - Prometheus metrics (80+ metrics across 12 categories)
- pkg/health - Health monitoring (4 HTTP endpoints, enhanced checks, graceful degradation)

Internal Systems:
- internal/licensing - License validation (KACHING integration, cluster leases, fail-closed)
- internal/hapui - Human Agent Portal UI (9 commands, HMMM wizard, UCXL browser, decision voting)
- internal/backbeat - P2P operation telemetry (6 phases, beat synchronization, health reporting)

Documentation Statistics (Phase 3):
- 10 packages documented (~18,000 lines)
- 31 PubSub message types cataloged
- 80+ Prometheus metrics documented
- Complete API references with examples
- Integration patterns and best practices

Key Features Documented:
- Election: 5 triggers, candidate scoring (5 weighted components), stability windows
- Coordination: AI-powered dependency detection, cross-repo sessions, escalation handling
- PubSub: Topic patterns, message envelopes, SHHH redaction, Hypercore logging
- Metrics: All metric types with labels, Prometheus scrape config, alert rules
- Health: Liveness vs readiness, critical checks, Kubernetes integration
- Licensing: Grace periods, circuit breaker, cluster lease management
- HAP UI: Interactive terminal commands, HMMM composition wizard, web interface (beta)
- BACKBEAT: 6-phase operation tracking, beat budget estimation, drift detection

Implementation Status Marked:
- ✅ Production: Election, metrics, health, licensing, pubsub, p2p, discovery, coordinator
- 🔶 Beta: HAP web interface, BACKBEAT telemetry, advanced coordination
- 🔷 Alpha: SLURP election scoring
- ⚠️ Experimental: Meta-coordination, AI-powered dependency detection

Progress: 22/62 files complete (35%)

Next Phase: AI providers, SLURP system, API layer, reasoning engine

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

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

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