fix: validate platform keys at the gate and stop auto-register

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

tests/test_platform_dynamic.py

@@ -74,3 +74,60 @@ class TestResolvePlatformKeyDynamicParsing:
         clean_db.commit()
         result = resolve_platform_key_dynamic("bad_alias", conn=clean_db)
         assert result.platform_key == "bad_alias"
+
+
+class TestPlatformKeyFormatAndAmbiguity:
+    def test_format_rejects_mixed_case(self):
+        from util.platforms import is_valid_platform_key_format
+
+        assert is_valid_platform_key_format("haokan") is True
+        assert is_valid_platform_key_format("HaoKan") is False
+        assert is_valid_platform_key_format("hao_kan") is True
+
+    def test_deepseek_display_resolves_to_key(self, clean_db):
+        from util.platforms import resolve_platform_key_dynamic
+
+        result = resolve_platform_key_dynamic("DeepSeek", conn=clean_db)
+        assert result.ok
+        assert result.platform_key == "deepseek"
+
+    def test_douyin_alias_still_unique(self, clean_db):
+        from util.platforms import resolve_platform_key_dynamic
+
+        result = resolve_platform_key_dynamic("抖音", conn=clean_db)
+        assert result.platform_key == "douyin"
+
+    def test_wechat_key_wins(self, clean_db):
+        from util.platforms import resolve_platform_key_dynamic
+
+        result = resolve_platform_key_dynamic("wechat", conn=clean_db)
+        assert result.ok
+        assert result.platform_key == "wechat"
+
+    def test_gongzhonghao_is_ambiguous(self, clean_db):
+        from util.platforms import resolve_platform_key_dynamic
+
+        result = resolve_platform_key_dynamic("公众号", conn=clean_db)
+        assert not result.ok
+        assert result.error_code == "AMBIGUOUS_PLATFORM"
+        assert "wechat" in (result.message or "")
+        assert "wechat_mp" in (result.message or "")
+
+    def test_unregistered_lookalike_key(self, clean_db):
+        from util.platforms import resolve_platform_key_dynamic
+
+        result = resolve_platform_key_dynamic("HaoKan", conn=clean_db)
+        assert result.error_code == "INVALID_PLATFORM_KEY"
+        assert "platform ensure" in (result.message or "")
+
+    def test_unregistered_valid_key_not_inserted(self, clean_db):
+        from util.platforms import resolve_platform_key_dynamic
+
+        result = resolve_platform_key_dynamic("hao_kan", conn=clean_db)
+        assert result.error_code == "PLATFORM_NOT_REGISTERED"
+        assert "已拒绝写入" in (result.message or "")
+        count = clean_db.execute(
+            "SELECT COUNT(*) FROM platforms WHERE platform_key = 'hao_kan'"
+        ).fetchone()[0]
+        assert count == 0
+