feat(ceus): 任务书 02 第一阶段——底层和分割之前的算法；修复 C14

任务书 01 遗留修复（C14）：
- library 新增 check_key_image(path)：关键图能逐像素保真重编码时返回 None，否则返回原因；
  _write_clean_png 的判断移过去，自身保留断言性质报错（走到这里说明 build 漏了检查）。
- build 写库前对每例调用，返回原因的整例跳过，记 C14「关键图能原样重编码」，涉及值写原因。
- 原来三条「关键图格式不对整次构建停下」的测试改为整例跳过，另加非 PNG、library 漏检报错两条。
- 结构.md 第八部分、guides/装配两个库.md 相应几行改掉。

第一阶段（src/cadx/ceus/）：
- 照搬旧 geometry、video_decoder、research_config、split_screen、green_prompt、prompt_frames、
  mapping，去掉产品层，注释改中文。
- 配置类去掉全部默认值，strict、extra=forbid、frozen；新建 config/ceus.yaml（paths、ceus 两段），
  数值照抄旧 yaml，逐项注明出处。删去 source_view/target_view、effective_region、mapping 锚点；
  旧代码写死的分屏抽帧数 25 和搜索区间 (0.35, 0.65) 改成配置，值不变。
- 视频解码改为按路径用 cv2 逐帧读。
- 坐标换算改为两个视图矩形左上角之差，不再用按某种宽度写死的锚点。
- 造影画面在哪一半：两半各自选提示帧，恰好一半有才定，否则抛 ContrastSideError（CeusCaseError
  子类，带步号和原因，供第三阶段记 failed.csv）。
- 旧测试照搬（改 import 与配置读取方式），因上述改动不再成立的删去；新增两处修改的手算测试。
- import-linter 加「ceus 不引用其他 cadx 模块」。依赖加 numpy、opencv-python-headless。

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_build_outputs.py

@@ -12,11 +12,13 @@ from PIL import Image
 from cadx.answers import read_aliases, read_diagnoses
 from cadx.build import make_aliases, run_build
 from cadx.library import (
+    LibraryCase,
     list_aliases,
     read_clinical,
     read_mr,
     read_ultrasound,
     scan_for_leaks,
+    write_library,
 )
 from fake_delivery import (
     CLINICAL_HEADER,
@@ -218,24 +220,59 @@ def _build_with_key_image(tmp_path: Path, image: Image.Image) -> None:
     run_build(write_config(tmp_path, root, 1, None), REPO_ROOT, NOW)
 
 
-def test_key_image_16_bit_source_stops_build(tmp_path: Path) -> None:
-    image = Image.new("I;16", (4, 4))
-    with pytest.raises(ValueError, match=r"U002_key\.png"):
-        _build_with_key_image(tmp_path, image)
-    assert not (tmp_path / "library" / f"{NOW:%Y%m%d-%H%M%S}").exists()
-    assert [p for p in (tmp_path / "library").iterdir() if not p.name.endswith(".partial")] == []
+def _assert_key_image_skipped(tmp_path: Path, reason: str) -> None:
+    """002 这一例记 C14 跳过、涉及值是原因；001 照常进库。"""
+    (library_dir,) = list((tmp_path / "library").iterdir())
+    answers_dir = tmp_path / "answers" / library_dir.name
+    assert [r.case_no for r in read_aliases(answers_dir)] == ["001"]
+    assert len(list_aliases(library_dir)) == 1
+    skipped = _csv_rows(answers_dir / "skipped.csv")
+    assert [row[:4] for row in skipped[1:]] == [
+        ["002", "C14", "关键图能原样重编码", "CEUS_agent/002/U002_key.png"]
+    ]
+    assert json.loads(skipped[1][5]) == reason
 
 
-def test_key_image_with_transparency_stops_build(tmp_path: Path) -> None:
+def test_key_image_16_bit_source_skips_case(tmp_path: Path) -> None:
+    _build_with_key_image(tmp_path, Image.new("I;16", (4, 4)))
+    _assert_key_image_skipped(tmp_path, "位深 16、颜色类型 0 不能逐像素保真重编码")
+
+
+def test_key_image_with_transparency_skips_case(tmp_path: Path) -> None:
     image = Image.new("RGB", (4, 4))
     image.info["transparency"] = (0, 0, 0)
-    with pytest.raises(ValueError, match=r"U002_key\.png"):
-        _build_with_key_image(tmp_path, image)
+    _build_with_key_image(tmp_path, image)
+    _assert_key_image_skipped(tmp_path, "带 tRNS 透明色，重编码会丢透明")
 
 
-def test_key_image_palette_source_stops_build(tmp_path: Path) -> None:
-    with pytest.raises(ValueError, match=r"U002_key\.png"):
-        _build_with_key_image(tmp_path, Image.new("P", (4, 4)))
+def test_key_image_palette_source_skips_case(tmp_path: Path) -> None:
+    _build_with_key_image(tmp_path, Image.new("P", (4, 4)))
+    # 只有一种颜色的调色板图，Pillow 存成 1 位。
+    _assert_key_image_skipped(tmp_path, "位深 1、颜色类型 3 不能逐像素保真重编码")
+
+
+def test_key_image_not_png_skips_case(tmp_path: Path) -> None:
+    root = make_delivery(2).write(tmp_path / "delivery")
+    Image.new("RGB", (4, 4)).save(root / "CEUS_agent" / "002" / "U002_key.png", format="JPEG")
+    run_build(write_config(tmp_path, root, 1, None), REPO_ROOT, NOW)
+    _assert_key_image_skipped(tmp_path, "不是 PNG")
+
+
+def test_write_library_rejects_unchecked_key_image(tmp_path: Path) -> None:
+    """build 漏了 C14 检查时，library 写图那一步报错停下。"""
+    source = tmp_path / "key.png"
+    Image.new("P", (4, 4)).save(source, format="PNG")
+    target = tmp_path / "out"
+    target.mkdir()
+    case = LibraryCase(
+        alias="abcd",
+        clinical_fields={},
+        ultrasound_report="",
+        key_image_source=source,
+        mr_report="",
+    )
+    with pytest.raises(ValueError, match="check_key_image"):
+        write_library(target, "b", "c", True, {}, False, (), None, [case])
 
 
 def test_key_image_one_bit_kept_as_is(tmp_path: Path) -> None: