refactor: Phase 3 拆分 generate 流水线并补全测试

提取 collect/formatters/themes 等 pipeline 模块，新增 wecom 分条、RSS、delta、Agent 工作流测试。

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_wecom_split.py

@@ -0,0 +1,34 @@
+from __future__ import annotations
+
+from daily.wecom_split import split_wecom_messages
+
+
+def test_split_wecom_messages_keeps_short_text():
+    text = "📰 **早报 · 2026-07-03**\n\n短内容"
+    parts = split_wecom_messages(text, limit=4096)
+    assert parts == [text]
+
+
+def test_split_wecom_messages_adds_part_footer():
+    section = "📰 **早报**\n\n" + ("正文行\n" * 200)
+    parts = split_wecom_messages(section, limit=600)
+    assert len(parts) > 1
+    assert all(len(part.encode("utf-8")) <= 600 for part in parts)
+    assert parts[0].endswith("1/" + str(len(parts)))
+
+
+def test_split_sections_on_emoji_headers():
+    from daily.wecom_split import _split_sections
+
+    text = "\n\n".join(
+        [
+            "📰 **早报 · 2026-07-03**",
+            "💡 **今日速览**\n- item one\n- item two",
+            "🌍 **国际 AI 时讯**\n1. [Headline](https://example.com)",
+        ]
+    )
+    sections = _split_sections(text)
+    assert len(sections) == 3
+    assert sections[0].startswith("📰")
+    assert sections[1].startswith("💡")
+    assert sections[2].startswith("🌍")