feat: add classifier routing strategy with LLM complexity rating

internal/router/heuristic.go

@@ -1,7 +1,6 @@
 package router
 
 import (
-	"context"
 	"encoding/json"
 	"strings"
 
@@ -65,9 +64,3 @@ func routeHeuristic(group db.ModelGroup, targets []string, userMessage string) (
 		Reason:        reason,
 	}, nil
 }
-
-// routeClassifier is a stub — real implementation in classifier.go (Task 3).
-// Falls back to heuristic routing for now.
-func routeClassifier(ctx context.Context, classify ClassifierFunc, group db.ModelGroup, targets []string, userMessage string) (*Decision, error) {
-	return routeHeuristic(group, targets, userMessage)
-}