v0.6.0: Cluster Visualization

v0.6.0 — Cluster Visualization + Web Dashboard + OpenTelemetry

New Features

• Cluster Visualization — topology graph, metrics panel, timeline event stream
  • GET /api/v1/cluster/topology — cluster topology (nodes, tasks, leases)
  • GET /api/v1/cluster/metrics — aggregated metrics
  • GET /api/v1/cluster/timeline — event timeline
  • GET /api/v1/cluster/viz — combined visualization data
• Web Dashboard — embedded static HTML/CSS/JS dashboard
  • GET /dashboard/ — dashboard entry point
• OpenTelemetry — distributed tracing (OTLP/gRPC or stdout export)
• Prometheus metrics — /metrics endpoint with hac_ prefix

Quality

• Build clean, go vet clean
• All integration tests pass (25+ tests)
• Dashboard integration tests (15 tests)
• Visualization integration tests (10 tests)

Commits

• feat: OpenTelemetry integration (P2-4)
• feat: Web Dashboard implementation
• fix: promote prometheus/client_model to direct dependency
• test: add dashboard integration tests
• docs: update README for v0.6.0