Add session permission mode and confirmation detail

Why: The product needs a session mode and a place to show tool arguments on a confirmation card without inventing a second card type.
Evidence: GOWORK=off go test . passed. New fields use omitempty, so existing golden JSON stays the same.
Impact: Empty permission mode still means the profile policy. Clients that ignore unknown fields keep working.
Refs: feature/permission-hooks
Co-authored-by: Cursor <cursoragent@cursor.com>

hitl.go

@@ -23,6 +23,8 @@ type HITLCard struct {
 	// Blocked：阻断态（门禁不通过等）——确认入口禁用并给出出路；阻断本身进审计。
 	Blocked     bool   `json:"blocked,omitempty"`
 	BlockReason string `json:"blockReason,omitempty"`
+	// Detail 是确认卡上的参数预览或其他补充说明。
+	Detail string `json:"detail,omitempty"`
 }
 
 type HITLKind string