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>

daily/pipeline/themes.py

@@ -0,0 +1,53 @@
+"""主题检测与聚类。"""
+
+from __future__ import annotations
+
+from collections import defaultdict
+from typing import Any
+
+THEME_RULES: list[tuple[str, str, list[str]]] = [
+    ("🎬", "AI 多媒体 / 视频", ["runcomfy", "remotion", "video", "seedance", "inpaint", "lipsync"]),
+    ("🔧", "工程协作 / Skill 元能力", ["grill", "tdd", "architecture", "find-skills", "to-issues"]),
+    ("📱", "飞书 / Lark", ["lark", "feishu"]),
+    ("📣", "内容营销", ["viral", "tiktok", "instagram", "reels"]),
+    ("🎨", "设计 / 前端", ["frontend", "design", "ui-ux", "tailwind"]),
+]
+
+
+def detect_theme_line(feed: dict[str, Any]) -> str:
+    scores: dict[str, int] = defaultdict(int)
+    for board in ("topTrending", "topHot"):
+        for rank, item in enumerate(feed.get(board, [])[:10], 1):
+            haystack = " ".join(
+                [item.get("title", ""), item.get("source", ""), item.get("description", "")]
+            ).lower()
+            for _icon, label, keywords in THEME_RULES:
+                if any(k in haystack for k in keywords):
+                    scores[label] += max(1, 11 - rank)
+                    break
+    if not scores:
+        return "**今日主题**：Agent Skills 生态持续活跃"
+    return f"**今日主题**：{max(scores.items(), key=lambda x: x[1])[0]}"
+
+
+def theme_clusters(feed: dict[str, Any], limit: int = 5) -> list[tuple[str, list[str]]]:
+    from daily.pipeline.snapshot import skill_id
+
+    buckets: dict[str, list[str]] = defaultdict(list)
+    seen: set[str] = set()
+    for board in ("topTrending", "topHot"):
+        for item in feed.get(board, [])[:20]:
+            item_id = skill_id(item)
+            if item_id in seen:
+                continue
+            seen.add(item_id)
+            haystack = " ".join(
+                [item.get("title", ""), item.get("source", ""), item.get("description", "")]
+            ).lower()
+            for _icon, theme, keywords in THEME_RULES:
+                if any(k in haystack for k in keywords):
+                    label = f"**{item.get('title')}** (`{item.get('source')}`)"
+                    if label not in buckets[theme]:
+                        buckets[theme].append(label)
+                    break
+    return [(theme, examples[:limit]) for theme, examples in buckets.items() if examples]