fix(mention): address PR #45 review feedback (M1-M3, S1-S3)

M1: Remove '帮忙' from help_keywords to fix keyword priority bug
M3: Add unit tests for mention_utils (§25.7)
S1: Merge two 'if action == opened' blocks in _handle_issues
S2: Extract _send_review_mentions helper to deduplicate @mention code
S3: Remove redundant 'import re' inside conditional block

tests/unit/test_mention_utils.py

@@ -0,0 +1,129 @@
+"""mention_utils 单元测试 — §25.7 覆盖。"""
+
+import pytest
+
+from src.api.mention_utils import (
+    extract_mentions,
+    should_suppress_mention,
+    infer_intent,
+)
+
+
+# ---------------------------------------------------------------------------
+# extract_mentions
+# ---------------------------------------------------------------------------
+
+class TestExtractMentions:
+    """测试 @mention 提取逻辑。"""
+
+    def test_exact_match(self):
+        """@zhangfei-dev 精确匹配。"""
+        assert extract_mentions("@zhangfei-dev 请看一下", "someone") == ["zhangfei-dev"]
+
+    def test_chinese_alias(self):
+        """@张飞 中文别名匹配。"""
+        assert extract_mentions("@张飞 帮忙看看", "someone") == ["zhangfei-dev"]
+
+    def test_english_short_name(self):
+        """@zhangfei 英文短名匹配。"""
+        assert extract_mentions("@zhangfei 快来", "someone") == ["zhangfei-dev"]
+
+    def test_prefix_unique(self):
+        """@zhangf 前缀唯一匹配。"""
+        assert extract_mentions("@zhangf 来一下", "someone") == ["zhangfei-dev"]
+
+    def test_prefix_ambiguous_no_match(self):
+        """@z 前缀模糊，多个候选，不匹配。"""
+        assert extract_mentions("@z 看看", "someone") == []
+
+    def test_dedup_same_person(self):
+        """@张飞 @zhangfei-dev 同时出现去重。"""
+        result = extract_mentions("@张飞 @zhangfei-dev 来一下", "someone")
+        assert result == ["zhangfei-dev"]
+
+    def test_exclude_self(self):
+        """@zhangfei-dev 排除自己（sender=zhangfei-dev）。"""
+        assert extract_mentions("@zhangfei-dev 自己说", "zhangfei-dev") == []
+
+    def test_unknown_person(self):
+        """@unknown 不匹配任何 Agent。"""
+        assert extract_mentions("@unknown 你好", "someone") == []
+
+    def test_multiple_mentions(self):
+        """多个 @mention 返回多个 Agent。"""
+        result = set(extract_mentions("@张飞 @关羽 来讨论", "someone"))
+        assert result == {"zhangfei-dev", "guanyu-dev"}
+
+    def test_mention_with_hyphen_in_middle(self):
+        """@mention 后面紧跟标点也能识别。"""
+        result = extract_mentions("@赵云，请看下", "someone")
+        assert result == ["zhaoyun-data"]
+
+
+# ---------------------------------------------------------------------------
+# should_suppress_mention
+# ---------------------------------------------------------------------------
+
+class TestShouldSuppressMention:
+    """测试 @mention 通知抑制逻辑。"""
+
+    def test_suppress_when_in_list(self):
+        """被提及者在自动通知列表中 → 抑制。"""
+        assert should_suppress_mention("zhangfei-dev", ["zhangfei-dev", "guanyu-dev"]) is True
+
+    def test_not_suppress_when_not_in_list(self):
+        """被提及者不在自动通知列表中 → 不抑制。"""
+        assert should_suppress_mention("zhangfei-dev", ["guanyu-dev"]) is False
+
+    def test_suppress_empty_list(self):
+        """自动通知列表为空 → 不抑制。"""
+        assert should_suppress_mention("zhangfei-dev", []) is False
+
+
+# ---------------------------------------------------------------------------
+# infer_intent
+# ---------------------------------------------------------------------------
+
+class TestInferIntent:
+    """测试意图推断逻辑。
+
+    优先级：assign → collaborate → help → notify（默认）
+    """
+
+    def test_help_question_mark(self):
+        """疑问句 → help。"""
+        assert infer_intent("@赵云 数据格式是什么？") == "help"
+
+    def test_notify_plain_mention(self):
+        """纯通知（无关键词） → notify。"""
+        assert infer_intent("@关羽 这个 PR 涉及风控变更") == "notify"
+
+    def test_collaborate_please_help(self):
+        """'请帮忙' → collaborate（NOT help!）。"""
+        assert infer_intent("@庞统 请帮忙澄清需求") == "collaborate"
+
+    def test_assign_keywords(self):
+        """'交给你' → assign。"""
+        assert infer_intent("@张飞 前端部分交给你") == "assign"
+
+    def test_help_how_to(self):
+        """'如何' → help。"""
+        assert infer_intent("@姜维 如何部署这个服务") == "help"
+
+    def test_collaborate_please_review(self):
+        """'请review' → collaborate。"""
+        assert infer_intent("@司马懿 请review 这个方案") == "collaborate"
+
+    def test_notify_default(self):
+        """无任何关键词 → notify。"""
+        assert infer_intent("@赵云 已更新数据") == "notify"
+
+    def test_assign_takes_priority_over_help(self):
+        """assign 关键词优先于 help 关键词。"""
+        # "交给" in body → assign, even though "？" also present
+        assert infer_intent("@张飞 这个模块交给你，有问题？") == "assign"
+
+    def test_collaborate_takes_priority_over_help(self):
+        """collaborate 关键词优先于 help 关键词。"""
+        # "请帮忙" in body → collaborate, even though "？" absent
+        assert infer_intent("@赵云 请帮忙看看数据") == "collaborate"