fix(hop): skip priority short-circuit when multiple nodes share the same priority

When two or more nodes have an identical matcher rule they receive
identical default priority (rule string length). The priority shortcut
assumed the top-priority node was the single authoritative choice and
returned it directly, bypassing the selector (FailFilter, BackupFilter,
strategy) — so weight, round-robin, and hash were silently ignored.

Add a third condition: the top priority must be strictly greater than
the second-highest. When multiple nodes share the same highest priority
the selector applies normally for load balancing.

Add doc comments on NodeMatcherConfig.Priority explaining the three
semantic ranges (0=auto, negative=always-selector, positive=shortcut).

config/parsing/node/parse.go

@@ -176,6 +176,10 @@ func ParseNode(hop string, cfg *config.NodeConfig, log logger.Logger) (*chain.No
 		if rule := strings.TrimSpace(cfg.Matcher.Rule); rule != "" {
 			if matcher, err := routing.NewMatcher(rule); err == nil {
 				log.Debugf("new matcher for node %s with rule %s", cfg.Name, cfg.Matcher.Rule)
+				// Priority 0 means "use default": automatically set to the
+				// rule length so longer (more specific) rules outrank shorter
+				// ones. Use a negative priority to opt out of this behavior
+				// and always go through the selector.
 				if priority == 0 {
 					priority = len(cfg.Matcher.Rule)
 				}