Add boot sequencing to agent

The agent reads [[boot.sequence]] stages from its config and starts
services in dependency order before accepting gRPC connections. Each
stage waits for its services to pass health checks before proceeding:

- tcp: TCP connect to the container's mapped port
- grpc: standard gRPC health check

Foundation stage (stage 0): blocks and retries indefinitely if health
fails — all downstream services depend on it.
Non-foundation stages: log warning and proceed on failure.

Uses the recover logic to start containers from the registry, then
health-checks to verify readiness.

Config example:
  [[boot.sequence]]
  name = "foundation"
  services = ["mcias", "mcns"]
  timeout = "120s"
  health = "tcp"

Architecture v2 Phase 4 feature.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/config/agent.go

@@ -19,6 +19,23 @@ type AgentConfig struct {
 	MCNS      MCNSConfig      `toml:"mcns"`
 	Monitor   MonitorConfig   `toml:"monitor"`
 	Log       LogConfig       `toml:"log"`
+	Boot      BootConfig      `toml:"boot"`
+}
+
+// BootConfig holds the boot sequence for the master node.
+// Each stage's services must be healthy before the next stage starts.
+// Worker and edge nodes don't use this — they wait for the master.
+type BootConfig struct {
+	Sequence []BootStage `toml:"sequence"`
+}
+
+// BootStage defines a group of services that must be started and healthy
+// before the next stage begins.
+type BootStage struct {
+	Name     string   `toml:"name"`
+	Services []string `toml:"services"`
+	Timeout  Duration `toml:"timeout"`
+	Health   string   `toml:"health"` // "tcp", "grpc", or "http"
 }
 
 // MetacryptConfig holds the Metacrypt CA integration settings for