fix(tray): render Codex free-plan 30-day window in tray menu

The tray keeps its own tier-name whitelist (TIER_LABEL_GROUPS) independent
of the frontend TIER_I18N_KEYS. Its month group only listed "monthly", so a
free Codex account whose only tier is "30_day" produced empty labeled parts
→ format_subscription_summary returned None → the tray showed no quota, even
though the footer now does. That breaks the invariant the existing
gemini_summary_lite_only_still_renders test guards: any tier visible in the
footer must not leave the tray blank.

- Add TIER_THIRTY_DAY ("30_day") constant so the string is single-sourced
  across backend mapping, tray grouping, and the frontend whitelist
- Map 2_592_000s explicitly to it in window_seconds_to_tier_name
- Add TIER_THIRTY_DAY to the tray month ("m") group
- Add codex_summary_thirty_day_only_still_renders regression test

Follow-up to the review on #3651 / PR for the 30-day footer fix.

src-tauri/src/services/subscription.rs

@@ -312,6 +312,12 @@ pub const TIER_WEEKLY_LIMIT: &str = "weekly_limit";
 /// 映射到 `subscription.monthly`。
 pub const TIER_MONTHLY: &str = "monthly";
 
+/// Codex 免费方案的 30 天（月）滚动窗口 tier 名。付费方案的次要窗口是 7 天
+/// (`seven_day`)，免费方案则是 30 天。由 `window_seconds_to_tier_name` 产出、
+/// tray 的月分组渲染、前端 `TIER_I18N_KEYS` 映射到 `subscription.thirtyDay`
+/// 三处共用同一标识。见 #3651。
+pub const TIER_THIRTY_DAY: &str = "30_day";
+
 /// Gemini 用量分组名称（按模型而非时间窗口）。`classify_gemini_model` 输出。
 pub const TIER_GEMINI_PRO: &str = "gemini_pro";
 pub const TIER_GEMINI_FLASH: &str = "gemini_flash";
@@ -632,8 +638,12 @@ struct CodexUsageResponse {
 /// 根据窗口秒数映射到 tier 名称（与 Claude 的命名兼容以复用前端 i18n）
 fn window_seconds_to_tier_name(secs: i64) -> String {
     match secs {
-        18000 => "five_hour".to_string(),
-        604800 => "seven_day".to_string(),
+        18000 => TIER_FIVE_HOUR.to_string(),
+        604800 => TIER_SEVEN_DAY.to_string(),
+        // Codex 免费方案的 30 天窗口。显式映射到常量，与 tray 月分组、前端
+        // TIER_I18N_KEYS 保持同一标识（否则动态回退虽也得到 "30_day"，但字符串
+        // 分散在多处、易和托盘/前端白名单脱节）。见 #3651。
+        2_592_000 => TIER_THIRTY_DAY.to_string(),
         s => {
             let hours = s / 3600;
             if hours >= 24 {
@@ -1348,11 +1358,11 @@ mod tests {
     #[test]
     fn window_seconds_map_to_expected_tier_names() {
         // 官方特例窗口
-        assert_eq!(window_seconds_to_tier_name(18000), "five_hour");
-        assert_eq!(window_seconds_to_tier_name(604800), "seven_day");
+        assert_eq!(window_seconds_to_tier_name(18000), TIER_FIVE_HOUR);
+        assert_eq!(window_seconds_to_tier_name(604800), TIER_SEVEN_DAY);
         // Codex 免费方案的次要窗口是 30 天（30 * 24 * 3600 = 2_592_000 秒）。
-        // 前端 TIER_I18N_KEYS 需要有对应的 "30_day" 才能展示，见 #3651。
-        assert_eq!(window_seconds_to_tier_name(2_592_000), "30_day");
+        // 前端 TIER_I18N_KEYS 与 tray 月分组都需要认得 "30_day"，见 #3651。
+        assert_eq!(window_seconds_to_tier_name(2_592_000), TIER_THIRTY_DAY);
         // 其他窗口按小时/天回退命名
         assert_eq!(window_seconds_to_tier_name(3600), "1_hour");
         assert_eq!(window_seconds_to_tier_name(86400), "1_day");

src-tauri/src/tray.rs

@@ -19,8 +19,13 @@ const W_TIER_NAMES: &[&str] = &[
     crate::services::subscription::TIER_SEVEN_DAY_OPUS,
     crate::services::subscription::TIER_SEVEN_DAY_SONNET,
 ];
-// 火山方舟 Agent/Coding Plan 的月窗口（5h/周/月 三档）。
-const M_TIER_NAMES: &[&str] = &[crate::services::subscription::TIER_MONTHLY];
+// 月窗口分组：火山方舟 Agent/Coding Plan 的月窗口（5h/周/月 三档），
+// 以及 Codex 免费方案的 30 天窗口（#3651）——两者都归入 "m" 档，避免免费
+// Codex 账号在托盘里空白（前端 footer 能看到、托盘却不显示的不对称）。
+const M_TIER_NAMES: &[&str] = &[
+    crate::services::subscription::TIER_MONTHLY,
+    crate::services::subscription::TIER_THIRTY_DAY,
+];
 const GEMINI_PRO_TIER_NAMES: &[&str] = &[crate::services::subscription::TIER_GEMINI_PRO];
 const GEMINI_FLASH_TIER_NAMES: &[&str] = &[crate::services::subscription::TIER_GEMINI_FLASH];
 const GEMINI_FLASH_LITE_TIER_NAMES: &[&str] =
@@ -882,7 +887,7 @@ mod tests {
     use crate::services::subscription::{
         CredentialStatus, QuotaTier, SubscriptionQuota, TIER_FIVE_HOUR, TIER_GEMINI_FLASH,
         TIER_GEMINI_FLASH_LITE, TIER_GEMINI_PRO, TIER_MONTHLY, TIER_SEVEN_DAY, TIER_SEVEN_DAY_OPUS,
-        TIER_SEVEN_DAY_SONNET, TIER_WEEKLY_LIMIT,
+        TIER_SEVEN_DAY_SONNET, TIER_THIRTY_DAY, TIER_WEEKLY_LIMIT,
     };
 
     #[test]
@@ -964,6 +969,16 @@ mod tests {
         assert!(s.contains("l80%"), "expected l80% in {s}");
     }
 
+    #[test]
+    fn codex_summary_thirty_day_only_still_renders() {
+        // Codex 免费方案的唯一 tier 是 30 天窗口。前端 footer 已能显示（TIER_I18N_KEYS
+        // 有 "30_day"），托盘也必须能显示——否则就是这条不变量要防的非对称：footer
+        // 能看到、托盘却空白。30_day 归入 "m" 月分组。见 #3651。
+        let quota = make_quota("codex", true, vec![tier(TIER_THIRTY_DAY, 85.0)]);
+        let s = format_subscription_summary(&quota).expect("should format");
+        assert!(s.contains("m85%"), "expected m85% in {s}");
+    }
+
     #[test]
     fn gemini_summary_emoji_reflects_highest_tier_including_lite() {
         // lite 是利用率最高的那条 → emoji 必须是红色，不能被 pro/flash 掩盖。