perf(data): compact immutable snapshots with current execution rules

crates/fidc-core/tests/core_rules.rs

@@ -15,7 +15,7 @@ fn d(year: i32, month: u32, day: u32) -> NaiveDate {
 fn candidate() -> CandidateEligibility {
     CandidateEligibility {
         date: d(2024, 1, 3),
-        symbol: "000001.SZ".to_string(),
+        symbol: "000001.SZ".into(),
         is_st: false,
         is_star_st: false,
         is_new_listing: false,
@@ -31,7 +31,7 @@ fn candidate() -> CandidateEligibility {
 fn snapshot(open: f64, upper_limit: f64, lower_limit: f64) -> DailyMarketSnapshot {
     DailyMarketSnapshot {
         date: d(2024, 1, 3),
-        symbol: "000001.SZ".to_string(),
+        symbol: "000001.SZ".into(),
         timestamp: Some("2024-01-03 10:18:00".to_string()),
         day_open: open,
         open,
@@ -256,7 +256,7 @@ fn china_rule_hooks_allow_sell_when_last_price_is_above_lower_limit() {
 
     let snapshot = DailyMarketSnapshot {
         date: d(2024, 4, 7),
-        symbol: "000001.SZ".to_string(),
+        symbol: "000001.SZ".into(),
         timestamp: Some("2024-04-07 10:18:00".to_string()),
         day_open: 2.53,
         open: 2.53,