fix(util): align reasoning effort handling with registry

internal/util/thinking.go

@@ -113,45 +113,3 @@ func defaultReasoningLevel(levels []string) string {
 	}
 	return ""
 }
-
-// standardReasoningEfforts defines the canonical set of reasoning effort levels.
-// This serves as the single source of truth for valid effort values.
-var standardReasoningEfforts = []string{"none", "auto", "minimal", "low", "medium", "high", "xhigh"}
-
-// IsValidReasoningEffort checks if the given effort string is a valid reasoning effort level.
-// This is a registry-independent check against the standard effort levels.
-func IsValidReasoningEffort(effort string) bool {
-	if effort == "" {
-		return false
-	}
-	lowered := strings.ToLower(strings.TrimSpace(effort))
-	for _, e := range standardReasoningEfforts {
-		if e == lowered {
-			return true
-		}
-	}
-	return false
-}
-
-// NormalizeReasoningEffort normalizes a reasoning effort string to its canonical form.
-// It first tries registry-based normalization if a model is provided, then falls back
-// to the standard effort levels. Returns empty string and false if invalid.
-func NormalizeReasoningEffort(model, effort string) (string, bool) {
-	if effort == "" {
-		return "", false
-	}
-	lowered := strings.ToLower(strings.TrimSpace(effort))
-
-	if model != "" {
-		if normalized, ok := NormalizeReasoningEffortLevel(model, effort); ok {
-			return normalized, true
-		}
-	}
-
-	for _, e := range standardReasoningEfforts {
-		if e == lowered {
-			return e, true
-		}
-	}
-	return "", false
-}