fix(mihomo): name the Singapore nodes instead of matching 新

The single-char keyword also matched 新西兰, so the Singapore group held a New
Zealand node and url-test flipped the exit country mid-session.

modules/nixos/desktop/networking/mihomo/policy.yaml

@@ -14,8 +14,9 @@
 # `filter` (Go regex, case-insensitive). The generator also adds "🌍 其他地区"
 # (manual, everything not matched below) and "🌐 全部地区" (manual, all nodes);
 # AUTO is the all-node auto pick. Edit the regions freely; the single-char
-# keywords (港/台/日/新/美/韩) deliberately catch naming variants like
-# 美西, 日服 and 狮城.
+# keywords (港/台/日/美/韩) deliberately catch naming variants like 美西, 日服
+# and 狮城. Spell a country out where one character would also catch a
+# neighbour: 新 alone catches 新西兰.
 node_groups:
   - name: "🇭🇰 香港"
     filter: "(?i)(港|hk|hong ?kong|🇭🇰)"
@@ -24,7 +25,7 @@ node_groups:
   - name: "🇯🇵 日本"
     filter: "(?i)(日|jp|japan|东京|🇯🇵)"
   - name: "🇸🇬 新加坡"
-    filter: "(?i)(新|狮城|sg|singapore|🇸🇬)"
+    filter: "(?i)(新加坡|狮城|sg|singapore|🇸🇬)"
   - name: "🇰🇷 韩国"
     filter: "(?i)(韩|kr|korea|🇰🇷)"
   - name: "🇺🇸 美国"