feat(unified-render): Phase 2 - Feature Flag + RenderAdapter 适配层

- 新增 RENDER_ENGINE 配置项（legacy/unified），支持运行时切换渲染引擎
- 新建 RenderAdapter 适配层：EditPlan + EditPlanClips → ResolvedClip 转换，素材下载，进度回调
- compose_video 任务改造：根据 RENDER_ENGINE 配置选择旧引擎或新引擎
- 新引擎结果回写字段对齐（engine/width/height/file_size）
- 新增 16 个单元测试，validate_plan/render_plan/download_assets 全覆盖

apps/worker/video_processing/render_adapter.py

@@ -0,0 +1,289 @@
+"""统一渲染引擎适配层 — Phase 2.
+
+将 EditPlan + EditPlanClips（来自 DB）适配为 UnifiedRenderService 的输入格式，
+封装素材下载、渲染执行、结果上传的完整流程。
+
+职责：
+  1. 从 DB 读取 EditPlan + EditPlanClips
+  2. 下载素材到本地，构建 asset_path_map
+  3. 调用 UnifiedRenderService 执行渲染
+  4. 上传渲染结果到 OSS
+  5. 支持进度回调（对接 JobService）
+"""
+
+from __future__ import annotations
+
+import logging
+import tempfile
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Any, Callable
+
+from sqlalchemy.orm import Session
+
+from packages.adapters.sqlalchemy_impl.edit_plan_clip_repository import (
+    SQLAlchemyEditPlanClipRepository,
+)
+from packages.adapters.sqlalchemy_impl.edit_plan_repository import (
+    SQLAlchemyEditPlanRepository,
+)
+from packages.domain.edit_plan import EditPlan, EditPlanStatus
+from packages.domain.edit_plan_clip import EditPlanClip, EditPlanClipStatus
+from video_processing.oss_helpers import download_asset, upload_to_oss
+from video_processing.unified_render_service import (
+    RenderResult,
+    UnifiedRenderService,
+)
+
+logger = logging.getLogger(__name__)
+
+
+# ── 数据结构 ──────────────────────────────────────────────────────────────────
+
+
+@dataclass
+class RenderAdapterResult:
+    """渲染适配结果。"""
+
+    success: bool
+    output_url: str = ""
+    output_path: Path | None = None
+    duration: float = 0.0
+    file_size: int = 0
+    width: int = 0
+    height: int = 0
+    clip_count: int = 0
+    error_message: str = ""
+
+
+ProgressCallback = Callable[[float, str], None]
+"""进度回调：(progress_0_100, stage_description) → None"""
+
+
+# ── 适配层主体 ────────────────────────────────────────────────────────────────
+
+
+class RenderAdapter:
+    """统一渲染引擎适配层。
+
+    桥接 EditPlan 领域模型与 UnifiedRenderService 图层模型。
+
+    用法::
+
+        adapter = RenderAdapter(db)
+        result = adapter.render_plan(
+            plan_id=plan_id,
+            job_id=job_id,
+            progress_cb=lambda p, s: job_service.update_progress(job_id, p, s),
+        )
+    """
+
+    def __init__(self, db: Session) -> None:
+        self._db = db
+        self._plan_repo = SQLAlchemyEditPlanRepository(db)
+        self._clip_repo = SQLAlchemyEditPlanClipRepository(db)
+
+    # ── 公开方法 ──────────────────────────────────────────────────────────
+
+    def render_plan(
+        self,
+        plan_id: str,
+        *,
+        job_id: str = "",
+        work_dir: Path | None = None,
+        progress_cb: ProgressCallback | None = None,
+    ) -> RenderAdapterResult:
+        """渲染一个 EditPlan。
+
+        完整流程：
+        1. 加载计划与片段
+        2. 下载素材
+        3. 执行统一渲染
+        4. 上传结果
+
+        Args:
+            plan_id: EditPlan ID
+            job_id: 关联的 Job ID（用于结果存储路径）
+            work_dir: 工作目录，不传则使用临时目录
+            progress_cb: 进度回调函数
+
+        Returns:
+            RenderAdapterResult
+        """
+        temp_dir = None
+        try:
+            # 0. 准备工作目录
+            if work_dir is None:
+                temp_dir = tempfile.mkdtemp(prefix="render_")
+                work_dir = Path(temp_dir)
+            work_dir.mkdir(parents=True, exist_ok=True)
+
+            self._report_progress(progress_cb, 5.0, "加载剪辑计划")
+
+            # 1. 加载计划与片段
+            plan = self._plan_repo.get(plan_id)
+            if plan is None:
+                return RenderAdapterResult(
+                    success=False,
+                    error_message=f"剪辑计划不存在: {plan_id}",
+                )
+
+            clips = self._clip_repo.list_by_plan(plan_id, skip=0, limit=10000)
+            ready_clips = [c for c in clips if c.status == EditPlanClipStatus.READY and c.asset_id]
+            ready_clips.sort(key=lambda c: c.order)
+
+            if not ready_clips:
+                return RenderAdapterResult(
+                    success=False,
+                    error_message="没有可渲染的就绪片段",
+                    clip_count=0,
+                )
+
+            logger.info(
+                "开始渲染: plan_id=%s job_id=%s ready_clips=%d",
+                plan_id,
+                job_id,
+                len(ready_clips),
+            )
+
+            self._report_progress(progress_cb, 15.0, f"下载素材（{len(ready_clips)} 个）")
+
+            # 2. 下载素材
+            asset_path_map = self._download_assets(ready_clips, work_dir)
+            if not asset_path_map:
+                return RenderAdapterResult(
+                    success=False,
+                    error_message="所有素材下载失败",
+                    clip_count=len(ready_clips),
+                )
+
+            self._report_progress(progress_cb, 40.0, "执行视频渲染")
+
+            # 3. 执行统一渲染
+            render_svc = UnifiedRenderService(
+                plan=plan,
+                clips=ready_clips,
+                asset_path_map=asset_path_map,
+                work_dir=work_dir,
+            )
+            result = render_svc.render()
+
+            self._report_progress(progress_cb, 80.0, "上传渲染结果")
+
+            # 4. 上传结果
+            storage_key = f"rendered/{plan_id}/{job_id or plan_id}.mp4"
+            output_url = upload_to_oss(result.output_path, storage_key)
+
+            self._report_progress(progress_cb, 100.0, "渲染完成")
+
+            return RenderAdapterResult(
+                success=True,
+                output_url=output_url or "",
+                output_path=result.output_path,
+                duration=result.duration,
+                file_size=result.file_size,
+                width=result.width,
+                height=result.height,
+                clip_count=len(ready_clips),
+            )
+
+        except Exception as exc:
+            logger.exception("渲染失败: plan_id=%s", plan_id)
+            return RenderAdapterResult(
+                success=False,
+                error_message=str(exc)[:500],
+            )
+        finally:
+            # 清理临时目录
+            if temp_dir:
+                import shutil
+
+                try:
+                    shutil.rmtree(temp_dir, ignore_errors=True)
+                except Exception:
+                    pass
+
+    def validate_plan(self, plan_id: str) -> tuple[bool, list[str], list[str], int, int]:
+        """校验计划是否可渲染（兼容 VideoComposeService.validate_compose 接口）。
+
+        Returns:
+            (valid, errors, warnings, ready_clip_count, total_clip_count)
+        """
+        errors: list[str] = []
+        warnings: list[str] = []
+
+        plan = self._plan_repo.get(plan_id)
+        if plan is None:
+            return False, [f"剪辑计划不存在: {plan_id}"], [], 0, 0
+
+        if plan.status not in (EditPlanStatus.EDITING, EditPlanStatus.RENDERING):
+            errors.append(f"计划状态不正确，需要 editing 或 rendering，当前: {plan.status}")
+
+        clips = self._clip_repo.list_by_plan(plan_id, skip=0, limit=10000)
+        if not clips:
+            errors.append("计划没有任何片段")
+            return False, errors, warnings, 0, 0
+
+        clips.sort(key=lambda c: c.order)
+
+        ready_count = 0
+        pending_count = 0
+        no_asset_count = 0
+
+        for clip in clips:
+            if clip.status == EditPlanClipStatus.READY:
+                ready_count += 1
+                if not clip.asset_id:
+                    errors.append(f"片段 {clip.id} (order={clip.order}) 没有分配素材")
+                    no_asset_count += 1
+            elif clip.status == EditPlanClipStatus.PENDING:
+                pending_count += 1
+            elif clip.status == EditPlanClipStatus.FAILED:
+                warnings.append(f"片段 {clip.id} (order={clip.order}) 状态为 failed，已跳过")
+
+        if ready_count == 0:
+            errors.append("没有就绪（ready）的片段可以合成")
+
+        if pending_count > 0:
+            warnings.append(f"有 {pending_count} 个片段仍处于 pending 状态")
+
+        return len(errors) == 0, errors, warnings, ready_count, len(clips)
+
+    # ── 内部方法 ──────────────────────────────────────────────────────────
+
+    @staticmethod
+    def _report_progress(progress_cb: ProgressCallback | None, progress: float, stage: str) -> None:
+        """上报进度。"""
+        if progress_cb is not None:
+            try:
+                progress_cb(progress, stage)
+            except Exception:
+                logger.exception("进度回调失败")
+
+    @staticmethod
+    def _download_assets(clips: list[EditPlanClip], work_dir: Path) -> dict[str, Path]:
+        """下载片段素材到本地，返回 asset_id → local_path 映射。
+
+        只保留下载成功的素材。
+        """
+        asset_dir = work_dir / "assets"
+        asset_dir.mkdir(exist_ok=True)
+
+        asset_path_map: dict[str, Path] = {}
+
+        for clip in clips:
+            asset_id = clip.asset_id
+            if not asset_id:
+                continue
+
+            # 生成安全的本地文件名
+            safe_name = f"clip_{clip.order:04d}_{abs(hash(asset_id)) % 100000:05d}.mp4"
+            local_path = asset_dir / safe_name
+
+            if download_asset(asset_id, local_path):
+                asset_path_map[asset_id] = local_path
+                logger.debug("素材下载成功: clip_id=%s asset_id=%s", clip.id, asset_id[:60])
+            else:
+                logger.warning("素材下载失败: clip_id=%s asset_id=%s", clip.id, asset_id[:60])
+
+        return asset_path_map