Generalize config prefix stripping and refactor improve CSV output

- Replace hardcoded v2c_/v1c_ prefix stripping with generic rsplit_once('_')
  approach that handles any prefix (v2b_, v3a_, etc.) while validating
  the suffix is exactly 3 ASCII digits
- Refactor write_improve_csv to emit one row per normalized config per car
  instead of a single aggregated row, giving visibility into all viable
  upgrade paths
- Add 4 new tests covering prefix stripping and improve CSV behavior

src/parsing/mod.rs

@@ -97,15 +97,17 @@ pub fn parse_car_times(
     // Process each configuration variant (111, 233, 323, etc.)
     if let Some(configurations) = json_data["data"].as_object() {
         for (raw_config, entry) in configurations {
-            // Strip version prefix (e.g., "v2c_" from "v2c_233") at read time.
-            // Downstream code only ever sees bare digit strings.
-            // Use explicit prefix matching to avoid mis-stripping keys that
-            // naturally contain underscores.
+            // Strip version prefix (e.g., "v2c_" from "v2c_233", "v2b_" from "v2b_111")
+            // at read time. Downstream code only ever sees bare digit strings.
+            // Generic approach: find the last '_' and take what follows it,
+            // but only if the remainder is exactly 3 ASCII digits. Otherwise
+            // keep the key unchanged (handles bare configs like "233" and
+            // unexpected formats gracefully).
             let config = raw_config
-                .strip_prefix("v2c_")
-                .or_else(|| raw_config.strip_prefix("v1c_"))
-                .unwrap_or(raw_config)
-                .to_string();
+                .rsplit_once('_')
+                .filter(|(_, suffix)| suffix.len() == 3 && suffix.bytes().all(|b| b.is_ascii_digit()))
+                .map(|(_, suffix)| suffix.to_string())
+                .unwrap_or_else(|| raw_config.clone());
             // Process timing data for each track
             if let Some(times) = entry["times"].as_object() {
                 for (track_id, details) in times {
@@ -636,6 +638,100 @@ mod tests {
         assert_eq!(translate_track_type("99"), "99");
     }
 
+    // =======================================================================
+    // Prefix stripping tests
+    // =======================================================================
+
+    #[test]
+    fn test_parse_car_times_strips_v2b_prefix() {
+        let ctx = AnalysisContext::new();
+        let car = Car {
+            rid: "TestCar_2020".to_string(),
+            brand: "TestBrand".to_string(),
+            only_name: "TestModel".to_string(),
+            year: 2020,
+            rq: 85,
+            prize: false,
+            guid: "guid_test".to_string(),
+        };
+
+        let dir = tempfile::tempdir().unwrap();
+        let times_dir = dir.path().to_str().unwrap();
+        let file_path = dir.path().join("TestCar_2020.json");
+
+        // Use "v2b_233" prefix — previously not stripped
+        let json_content = r#"{
+            "data": {
+                "v2b_233": {
+                    "times": {
+                        "laguna_a00": { "t": 100.0, "u": "Player1" }
+                    }
+                }
+            }
+        }"#;
+        fs::write(&file_path, json_content).unwrap();
+
+        let my_cars: HashSet<String> = HashSet::new();
+        parse_car_times(car, &my_cars, &ctx.best_cars, times_dir).unwrap();
+
+        // Verify the config was stripped to "233" (not "v2b_233")
+        let records = ctx.best_cars.get(&("Laguna Seca".to_string(), 85, "Dry".to_string())).unwrap();
+        assert_eq!(records[0].config, "233", "v2b_ prefix should be stripped");
+        assert_eq!(records[0].normalized_config, "233", "233 is already a final build");
+    }
+
+    #[test]
+    fn test_parse_car_times_strips_various_prefixes() {
+        let ctx = AnalysisContext::new();
+        let car = Car {
+            rid: "TestCar_2021".to_string(),
+            brand: "TestBrand".to_string(),
+            only_name: "TestModel".to_string(),
+            year: 2021,
+            rq: 90,
+            prize: false,
+            guid: "guid_test2".to_string(),
+        };
+
+        let dir = tempfile::tempdir().unwrap();
+        let times_dir = dir.path().to_str().unwrap();
+        let file_path = dir.path().join("TestCar_2021.json");
+
+        // Mix of prefix styles: v2c_, v1c_, v3a_, and bare
+        let json_content = r#"{
+            "data": {
+                "v2c_111": {
+                    "times": {
+                        "laguna_a00": { "t": 110.0, "u": "P1" }
+                    }
+                },
+                "v3a_233": {
+                    "times": {
+                        "laguna_a00": { "t": 95.0, "u": "P2" }
+                    }
+                },
+                "323": {
+                    "times": {
+                        "mnCity_a01": { "t": 88.0, "u": "P3" }
+                    }
+                }
+            }
+        }"#;
+        fs::write(&file_path, json_content).unwrap();
+
+        let my_cars: HashSet<String> = HashSet::new();
+        parse_car_times(car, &my_cars, &ctx.best_cars, times_dir).unwrap();
+
+        // Best on Laguna Seca should be the v3a_233 entry (95.0 beats 110.0)
+        let records = ctx.best_cars.get(&("Laguna Seca".to_string(), 90, "Dry".to_string())).unwrap();
+        assert_eq!(records[0].config, "233", "v3a_ prefix should be stripped");
+        assert_eq!(records[0].time, 95.0);
+
+        // Monaco Streets from bare "323"
+        let records = ctx.best_cars.get(&("Monaco Streets".to_string(), 90, "Wet".to_string())).unwrap();
+        assert_eq!(records[0].config, "323", "bare config should pass through");
+    }
+
     // =======================================================================
     // Constants tests
     // =======================================================================