覆盖文件缺 3D 段时按受控默认价补齐，不再把 3D 整段算成未配置

- 新增 backfill_legacy_model3d_pricing：旧覆盖文件整段没有 3D 时补上默认 JSON 的两段并告警
- 覆盖文件继续只承担种子与兜底，避免老种子文件把 3D 生成整段关掉
- 补用例覆盖覆盖文件缺 3D 段的读取

server-rs/crates/api-server/src/editor_generation_config.rs

@@ -6,6 +6,7 @@ use std::{
 };
 
 use serde::{Deserialize, Serialize};
+use tracing::warn;
 
 use crate::asset_billing::current_external_generation_billing_price_mud_points;
 use crate::tripo3d::pricing::{
@@ -391,6 +392,7 @@ fn load_editor_generation_pricing_from_candidates(
             serde_json::from_str::<EditorGenerationPricingConfig>(override_json.as_str())
                 .map_err(EditorGenerationPricingError::Json)?;
         backfill_legacy_sfx_pricing(&mut override_config, &config, source.as_ref())?;
+        backfill_legacy_model3d_pricing(&mut override_config, &config, source.as_ref());
         override_config.validate().map_err(|error| match error {
             EditorGenerationPricingError::Invalid(message) => {
                 EditorGenerationPricingError::Invalid(format!("{source}: {message}"))
@@ -429,6 +431,25 @@ fn backfill_legacy_sfx_pricing(
     Ok(())
 }
 
+/// 旧覆盖文件可能整段没有 3D 定价（3D 是后加的段）：缺失时用当前受控默认价补齐。
+///
+/// 覆盖文件只承担种子与兜底，不代表「3D 未配置」；这里补齐后，表内缺 3D 段的老行也能
+/// 按同一份默认价归一化，不会因为文件里没有这一段就把 3D 生成整段关掉。
+fn backfill_legacy_model3d_pricing(
+    config: &mut EditorGenerationPricingConfig,
+    fallback: &EditorGenerationPricingConfig,
+    source: &str,
+) {
+    if config.model3d.is_some() || fallback.model3d.is_none() {
+        return;
+    }
+    warn!(
+        source,
+        "覆盖文件缺少 3D 定价段，已按受控默认价补齐；确认 3D 价格后再从后台保存一次"
+    );
+    config.model3d = fallback.model3d.clone();
+}
+
 pub(crate) fn parse_editor_generation_pricing_json(
     json: &str,
     source: &str,
@@ -1136,6 +1157,36 @@ mod tests {
         std::fs::remove_dir_all(&temp_dir).expect("temp dir should remove");
     }
 
+    #[test]
+    fn editor_generation_pricing_legacy_override_backfills_missing_model3d_section() {
+        let temp_dir = unique_temp_dir("genarrative-pricing-legacy-model3d-test");
+        std::fs::create_dir_all(&temp_dir).expect("temp dir should create");
+        let override_path = temp_dir.join("editor-generation-pricing.override.json");
+        let mut legacy_config = default_runtime_pricing();
+        legacy_config.model3d = None;
+        legacy_config
+            .models
+            .get_mut(EDITOR_SOUND_EFFECT_MODEL_VIDU)
+            .expect("legacy sound effect pricing should exist")
+            .price = Some(17);
+        std::fs::write(
+            &override_path,
+            serde_json::to_string(&legacy_config).expect("legacy config should serialize"),
+        )
+        .expect("legacy override should write");
+
+        let loaded = load_editor_generation_pricing_from_paths(Some(&override_path))
+            .expect("legacy override should backfill the 3D section");
+
+        assert_eq!(
+            loaded.model3d,
+            default_runtime_pricing().model3d,
+            "覆盖文件缺 3D 段时应补上受控默认价"
+        );
+        assert_eq!(loaded.sound_effect_model_mud_points(Some("audio1.0")), 17);
+        std::fs::remove_dir_all(&temp_dir).expect("temp dir should remove");
+    }
+
     #[test]
     fn editor_generation_pricing_legacy_override_still_rejects_other_missing_models() {
         let temp_dir = unique_temp_dir("genarrative-pricing-legacy-required-model-test");