fix(usage): centralize cache-inclusive app set and cover grokbuild in cost backfill

The cost backfill hardcoded codex|gemini as cache-inclusive apps, so
grokbuild TOTAL-semantics rows were priced on full input tokens with
cache reads double-counted. Converge the writer (proxy logger and
calculator) and the backfill recompute onto a single
sql_helpers::is_cache_inclusive_app predicate backed by the existing
CACHE_INCLUSIVE_APP_TYPES constant, and add a regression test for the
grokbuild backfill path.

src-tauri/src/proxy/usage/calculator.rs

@@ -59,7 +59,8 @@ impl CostCalculator {
         pricing: &ModelPricing,
         cost_multiplier: Decimal,
     ) -> CostBreakdown {
-        let input_includes_cache_read = matches!(app_type, "codex" | "gemini" | "grokbuild");
+        let input_includes_cache_read =
+            crate::services::sql_helpers::is_cache_inclusive_app(app_type);
         Self::calculate_with_cache_semantics(
             usage,
             pricing,

src-tauri/src/proxy/usage/logger.rs

@@ -122,7 +122,7 @@ impl<'a> UsageLogger<'a> {
 
         let created_at = chrono::Utc::now().timestamp();
         let input_token_semantics =
-            if matches!(log.app_type.as_str(), "codex" | "gemini" | "grokbuild") {
+            if crate::services::sql_helpers::is_cache_inclusive_app(log.app_type.as_str()) {
                 INPUT_TOKEN_SEMANTICS_TOTAL
             } else {
                 INPUT_TOKEN_SEMANTICS_FRESH

src-tauri/src/services/sql_helpers.rs

@@ -16,7 +16,16 @@
 /// style provider not added here) shows up loudly as a too-low cache hit
 /// rate, which is easier to catch than the silent over-deduction that
 /// would happen with the opposite default.
-const CACHE_INCLUSIVE_APP_TYPES: &[&str] = &["codex", "gemini", "grokbuild"];
+/// 单一语义集（SSOT）：写入侧（proxy logger/calculator）、回填侧
+/// （usage_stats 成本重算）与展示侧（本文件的 SQL 归一）都必须引用这里，
+/// 防止同一语义散落多处后新增 app 时漏改（grokbuild 曾在回填侧漏掉）。
+/// 前端 `src/types/usage.ts` 的同名常量是跨语言的对应物，改动须同步。
+pub(crate) const CACHE_INCLUSIVE_APP_TYPES: &[&str] = &["codex", "gemini", "grokbuild"];
+
+/// `app_type` 的存储 `input_tokens` 是否已包含 cache read/write。
+pub(crate) fn is_cache_inclusive_app(app_type: &str) -> bool {
+    CACHE_INCLUSIVE_APP_TYPES.contains(&app_type)
+}
 
 pub(crate) const INPUT_TOKEN_SEMANTICS_LEGACY: i64 = 0;
 pub(crate) const INPUT_TOKEN_SEMANTICS_TOTAL: i64 = 1;

src-tauri/src/services/usage_stats.rs

@@ -1850,10 +1850,11 @@ impl Database {
         let million = rust_decimal::Decimal::from(1_000_000u64);
 
         // 与 CostCalculator::calculate_for_app 保持一致的计算逻辑：
-        // 1. 历史 Codex/Gemini 行只包含 cache read；新 total 行还包含 cache write。
+        // 1. 历史 cache-inclusive 行只包含 cache read；新 total 行还包含 cache write。
         // 2. Claude/Anthropic 的 input_tokens 已经是 fresh input，不能再次扣减
         // 3. 各项成本是基础成本（不含倍率），倍率只作用于最终总价
-        let cache_inclusive_app = matches!(log.app_type.as_str(), "codex" | "gemini");
+        let cache_inclusive_app =
+            crate::services::sql_helpers::is_cache_inclusive_app(log.app_type.as_str());
         let billable_input_tokens =
             if !cache_inclusive_app || log.input_token_semantics == INPUT_TOKEN_SEMANTICS_FRESH {
                 log.input_tokens as u64
@@ -2613,6 +2614,53 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn test_backfill_deducts_cache_read_for_grokbuild_total_rows() -> Result<(), AppError> {
+        // 回归：回填侧的 cache-inclusive 判定曾硬编码 codex|gemini 漏掉
+        // grokbuild，导致 TOTAL 行按全量 input 计价、cache_read 双算。
+        // 判定收敛到 sql_helpers::is_cache_inclusive_app 后按 450 fresh 计价。
+        let db = Database::memory()?;
+        {
+            let conn = lock_conn!(db.conn);
+            insert_usage_log(
+                &conn,
+                "grokbuild-total-backfill",
+                "grokbuild",
+                "_grok_session",
+                "grok-4.5",
+                "grok_session",
+                1000,
+                700,
+                100,
+                250,
+                0,
+                200,
+                "0",
+            )?;
+            conn.execute(
+                "UPDATE proxy_request_logs
+                 SET input_token_semantics = ?1
+                 WHERE request_id = 'grokbuild-total-backfill'",
+                [INPUT_TOKEN_SEMANTICS_TOTAL],
+            )?;
+        }
+
+        assert_eq!(db.backfill_missing_usage_costs()?, 1);
+
+        let conn = lock_conn!(db.conn);
+        let (input_cost, cache_read_cost, total_cost): (String, String, String) = conn.query_row(
+            "SELECT input_cost_usd, cache_read_cost_usd, total_cost_usd
+             FROM proxy_request_logs WHERE request_id = 'grokbuild-total-backfill'",
+            [],
+            |row| Ok((row.get(0)?, row.get(1)?, row.get(2)?)),
+        )?;
+        // grok-4.5 定价 2/6/0.50：input = (700-250)×2/1M，cache_read = 250×0.5/1M
+        assert_eq!(input_cost, "0.000900");
+        assert_eq!(cache_read_cost, "0.000125");
+        assert_eq!(total_cost, "0.001625");
+        Ok(())
+    }
+
     #[test]
     fn test_backfill_missing_usage_costs_uses_stored_multiplier() -> Result<(), AppError> {
         let db = Database::memory()?;