chore: 删除素材选取 random 模式

- generation_tasks.py: 删除 import random、if mode==random 分支、docstring 中 random 描述
- generation_task.py schema: description 移除 random=随机选取，count 描述仅保留 smart
- 选取入口条件 in ("random","smart") 改为 in ("smart",)
- test_asset_select_mode.py: 删除 TestSelectAssetsRandomMode 类（3个用例）
- domain/test_generation_task.py + test_wave77_generation_task.py: random→smart

不改：_calc_random_start_time（片段级随机）、smart_match.py、前端

apps/api/app/api/routes/generation_tasks.py

@@ -1,5 +1,4 @@
 import logging
-import random
 import uuid
 from typing import Any
 
@@ -116,8 +115,8 @@ def _select_assets_from_library(
 
     Args:
         assets: 素材库中所有素材（Asset 实体列表）
-        mode: 选取模式 — all=全部, random=随机, smart=智能匹配（多维度评分+多样性）
-        count: 选取数量，0 表示全部（仅 random/smart 模式有效）
+        mode: 选取模式 — all=全部, smart=智能匹配（多维度评分+多样性）
+        count: 选取数量，0 表示全部（仅 smart 模式有效）
 
     Returns:
         选中的素材 ID 列表
@@ -127,12 +126,6 @@ def _select_assets_from_library(
     if not ready_video_assets:
         return []
 
-    if mode == "random":
-        selected = (
-            ready_video_assets if count <= 0 else random.sample(ready_video_assets, min(count, len(ready_video_assets)))
-        )
-        return [a.id for a in selected]
-
     if mode == "smart":
         # 智能匹配：统一使用 packages/domain/smart_match.py 的多维评分+多样性选取
         # 评分维度：质量分(40%) + 时长适配(30%) + 新鲜度(20%) + 未使用加分(10%)
@@ -292,8 +285,8 @@ def create_generation_task(
                 mode=request.asset_select_mode,
                 count=request.asset_select_count,
             )
-    elif project_id and not resolved_asset_ids and request.asset_select_mode in ("random", "smart"):
-        # 项目级模式：未指定 asset_ids 且选择了 random/smart 模式时，也自动选取
+    elif project_id and not resolved_asset_ids and request.asset_select_mode in ("smart",):
+        # 项目级模式：未指定 asset_ids 且选择了 smart 模式时，也自动选取
         assets = asset_repository.find_by_project(project_id)
         if assets:
             resolved_asset_ids = _select_assets_from_library(

apps/api/app/schemas/generation_task.py

@@ -45,10 +45,10 @@ class CreateGenerationTaskRequest(BaseModel):
     # ── 素材库自动匹配 ──
     asset_select_mode: str = Field(
         default="all",
-        description="素材选取模式：all=全部ready视频, random=随机选取, smart=智能匹配（按质量/时长评分）",
+        description="素材选取模式：all=全部ready视频, smart=智能匹配（按质量/时长评分）",
     )
     asset_select_count: int = Field(
-        default=0, ge=0, le=100, description="选取数量，0表示全部（仅 random/smart 模式有效）"
+        default=0, ge=0, le=100, description="选取数量，0表示全部（仅 smart 模式有效）"
     )
     # ── 自动重试 ──
     auto_retry_enabled: bool = Field(

tests/unit/domain/test_generation_task.py

@@ -63,7 +63,7 @@ class TestGenerationTaskCreate:
             voice_ids=["v1"],
             created_by_user_id="  user1  ",
             source_edit_plan_id="  plan1  ",
-            asset_select_mode="random",
+            asset_select_mode="smart",
             batch_id="batch1",
         )
         assert task.project_id == "proj1"
@@ -76,7 +76,7 @@ class TestGenerationTaskCreate:
         assert task.voice_ids == ["v1"]
         assert task.created_by_user_id == "user1"
         assert task.source_edit_plan_id == "plan1"
-        assert task.asset_select_mode == "random"
+        assert task.asset_select_mode == "smart"
         assert task.batch_id == "batch1"
 
     def test_create_with_template_instead_of_project(self):

tests/unit/test_asset_select_mode.py

@@ -97,26 +97,6 @@ class TestSelectAssetsAllMode:
         assert result == []
 
 
-class TestSelectAssetsRandomMode:
-    """random 模式：随机选取 N 个。"""
-
-    def test_random_selects_exact_count(self):
-        assets = [_asset(f"a{i}", f"v{i}.mp4") for i in range(10)]
-        result = _select_assets_from_library(assets, mode="random", count=3)
-        assert len(result) == 3
-        assert all(rid in [a.id for a in assets] for rid in result)
-
-    def test_random_count_zero_returns_all(self):
-        assets = [_asset(f"a{i}", f"v{i}.mp4") for i in range(5)]
-        result = _select_assets_from_library(assets, mode="random", count=0)
-        assert len(result) == 5
-
-    def test_random_count_exceeds_total_returns_all(self):
-        assets = [_asset(f"a{i}", f"v{i}.mp4") for i in range(3)]
-        result = _select_assets_from_library(assets, mode="random", count=100)
-        assert len(result) == 3
-
-
 class TestSelectAssetsSmartMode:
     """smart 模式：使用 smart_match 多维评分（质量40%+时长30%+新鲜度20%+未使用10%）。"""
 

tests/unit/test_wave77_generation_task.py

@@ -116,7 +116,7 @@ class TestGenerationTaskCreate:
             voice_ids=["v1"],
             created_by_user_id="u1",
             source_edit_plan_id="ep1",
-            asset_select_mode="random",
+            asset_select_mode="smart",
             batch_id="batch_001",
             video_title="测试视频",
             resolution="1080p",
@@ -132,7 +132,7 @@ class TestGenerationTaskCreate:
         assert task.voice_ids == ["v1"]
         assert task.created_by_user_id == "u1"
         assert task.source_edit_plan_id == "ep1"
-        assert task.asset_select_mode == "random"
+        assert task.asset_select_mode == "smart"
         assert task.batch_id == "batch_001"
         assert task.video_title == "测试视频"
         assert task.resolution == "1080p"