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/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;