fix(vault): increase classify max_tokens to prevent truncated JSON

With 10 candidates, classify response can exceed 1024 tokens when
ctx descriptions are verbose, causing json unmarshal failures.
Bump to 2048 to accommodate worst-case 10-candidate responses.

internal/vault/enrich_classify.go

@@ -12,7 +12,7 @@ import (
 )
 
 const (
-	classifyMaxTokens       = 1024
+	classifyMaxTokens       = 2048
 	classifyTemperature     = 0.1
 	classifyCtxMaxLen       = 256 // max context string length stored in DB
 	classifySummaryMaxChars = 300 // max summary chars in prompt (validated: 300 for accuracy)