Phase C: Automated TLS cert provisioning for L7 routes

Add CertProvisioner that requests TLS certificates from Metacrypt's CA
API during deploy. When a service has L7 routes, the agent checks for
an existing cert, re-issues if missing or within 30 days of expiry,
and writes chain+key to mc-proxy's cert directory before registering
routes.

- Add MetacryptConfig to agent config (server_url, ca_cert, mount,
  issuer, token_path) with defaults and env overrides
- Add CertProvisioner (internal/agent/certs.go): REST client for
  Metacrypt IssueCert, atomic file writes, cert expiry checking
- Wire into Agent struct and deploy flow (before route registration)
- Add hasL7Routes/l7Hostnames helpers in deploy.go
- Fix pre-existing lint issues: unreachable code in portalloc.go,
  gofmt in servicedef.go, gosec suppressions, golangci v2 config
- Update vendored mc-proxy to fix protobuf init panic
- 10 new tests, make all passes with 0 issues

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

internal/agent/deploy.go

@@ -146,6 +146,14 @@ func (a *Agent) deployComponent(ctx context.Context, serviceName string, cs *mcp
 		}
 	}
 
+	// Provision TLS certs for L7 routes before registering with mc-proxy.
+	if a.Certs != nil && hasL7Routes(regRoutes) {
+		hostnames := l7Hostnames(serviceName, regRoutes)
+		if err := a.Certs.EnsureCert(ctx, serviceName, hostnames); err != nil {
+			a.Logger.Warn("failed to provision TLS cert", "service", serviceName, "err", err)
+		}
+	}
+
 	// Register routes with mc-proxy after the container is running.
 	if len(regRoutes) > 0 && a.Proxy != nil {
 		hostPorts, err := registry.GetRouteHostPorts(a.DB, serviceName, compName)
@@ -209,6 +217,37 @@ func ensureService(db *sql.DB, name string, active bool) error {
 	return registry.UpdateServiceActive(db, name, active)
 }
 
+// hasL7Routes reports whether any route uses L7 (TLS-terminating) mode.
+func hasL7Routes(routes []registry.Route) bool {
+	for _, r := range routes {
+		if r.Mode == "l7" {
+			return true
+		}
+	}
+	return false
+}
+
+// l7Hostnames returns the unique hostnames from L7 routes, applying
+// the default hostname convention when a route has no explicit hostname.
+func l7Hostnames(serviceName string, routes []registry.Route) []string {
+	seen := make(map[string]bool)
+	var hostnames []string
+	for _, r := range routes {
+		if r.Mode != "l7" {
+			continue
+		}
+		h := r.Hostname
+		if h == "" {
+			h = serviceName + ".svc.mcp.metacircular.net"
+		}
+		if !seen[h] {
+			seen[h] = true
+			hostnames = append(hostnames, h)
+		}
+	}
+	return hostnames
+}
+
 // ensureComponent creates the component if it does not exist, or updates its
 // spec if it does.
 func ensureComponent(db *sql.DB, c *registry.Component) error {