feat(writer): add build_contexts (template+rules -> GenerationContext list)

tests/test_phase5_context_builder.py

@@ -0,0 +1,30 @@
+from types import SimpleNamespace
+
+from genesis.data_models import ParsedTemplate, ChapterMarker
+from genesis.writer.context_builder import build_contexts
+from genesis.writer.models import GenerationContext
+
+
+def _ss():
+    template = ParsedTemplate(
+        file_name="t.docx",
+        sections=[
+            ChapterMarker(type="heading", name="はじめに", level=1),
+            ChapterMarker(type="placeholder", name="section:introduction", level=0),
+        ],
+        placeholders={},
+        styles={"defined": ["Heading1"], "used": ["Heading1", "Normal"]},
+    )
+    return SimpleNamespace(template=template)
+
+
+def test_build_contexts_maps_chapters():
+    ctxs = build_contexts(_ss(), samples_dir="nonexistent_dir_xyz")
+    assert len(ctxs) == 1
+    c = ctxs[0]
+    assert isinstance(c, GenerationContext)
+    assert c.chapter_id == "introduction"
+    assert c.write_rules == []          # 样本缺失 -> 空
+    assert c.design_rules == []
+    assert c.template_styles == {"Heading1", "Normal"}
+    assert c.template_marker.section_placeholder == "section:introduction"