feat: 首推理由行加 DAILY_FEATURED_REASON 开关

pick_why 本已渲染,现加开关默认开,空则省略(T6)。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_featured_reason.py

@@ -0,0 +1,55 @@
+# tests/test_featured_reason.py
+"""T6: 首推理由行(pick_why + DAILY_FEATURED_REASON 开关)测试。"""
+from __future__ import annotations
+
+import unittest
+from unittest import mock
+
+import daily.format_wecom as fw
+
+
+def _build(pick_why: str) -> str:
+    return fw.build_wecom_report(
+        date_str="2026-07-18",
+        time_str="08:50 (UTC+8)",
+        updated="2026-07-18",
+        highlights=[],
+        theme_line="**今日主题**：测试",
+        ai_news=None,
+        cn_ai_news=None,
+        merged_ai_news=None,
+        merged_tech_ai_news=None,
+        trending=[],
+        hot=[],
+        repos=[],
+        emerging=[],
+        topic_name="t",
+        topic_repos=[],
+        pick_command="npx skills add src/alpha",
+        pick_why=pick_why,
+        pick_title="alpha",
+        pick_url="https://x/a",
+        include_boards=False,
+    )
+
+
+class FeaturedReasonTests(unittest.TestCase):
+    def test_reason_shown_when_present_and_enabled(self):
+        with mock.patch.object(fw, "env_bool", return_value=True):
+            md = _build("昨日 star 增速第一")
+        self.assertIn("> 昨日 star 增速第一", md)
+
+    def test_reason_hidden_when_switch_off(self):
+        with mock.patch.object(fw, "env_bool", return_value=False):
+            md = _build("昨日 star 增速第一")
+        self.assertNotIn("> 昨日 star 增速第一", md)
+
+    def test_reason_omitted_when_empty(self):
+        with mock.patch.object(fw, "env_bool", return_value=True):
+            md = _build("")
+        self.assertIn("今日首推", md)
+        self.assertNotIn("> \n", md)
+
+
+if __name__ == "__main__":
+    unittest.main()