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_agent_workflow.py

@@ -0,0 +1,55 @@
+from __future__ import annotations
+
+import json
+
+
+def test_analyze_trends_parses_json(monkeypatch, isolated_output):
+    import daily.agent_workflow as agent
+    import daily.config as config
+
+    monkeypatch.setattr(config, "OUTPUT_DIR", isolated_output)
+    monkeypatch.setattr(agent, "OUTPUT_DIR", isolated_output)
+
+    monkeypatch.setattr(
+        agent,
+        "llm_chat",
+        lambda system, user: json.dumps(
+            {
+                "headline": "Skills 视频工具升温",
+                "opening": "今日 remotion 相关技能继续走强。",
+                "themes": [{"name": "视频", "summary": "Remotion 生态活跃"}],
+                "top_picks": [],
+                "signals": [],
+            },
+            ensure_ascii=False,
+        ),
+    )
+
+    llm_input = {"date": "2026-07-03", "skills_trending": []}
+    trends = agent.analyze_trends(llm_input, date_str="2026-07-03")
+
+    assert trends is not None
+    assert trends["headline"] == "Skills 视频工具升温"
+    assert (isolated_output / "2026-07-03.trends.json").exists()
+
+
+def test_write_wecom_report_extracts_markdown_block(monkeypatch):
+    import daily.agent_workflow as agent
+
+    monkeypatch.setattr(
+        agent,
+        "llm_chat",
+        lambda system, user: "```markdown\n📰 **早报 · 2026-07-03**\n\n正文\n```",
+    )
+
+    md = agent.write_wecom_report(
+        {"date": "2026-07-03"},
+        {"headline": "test", "opening": "open"},
+        date_str="2026-07-03",
+        time_str="09:30 (UTC+8)",
+        updated="2026-07-02",
+    )
+
+    assert md is not None
+    assert md.startswith("📰")
+    assert "正文" in md