refactor: modular architecture with unified error handling and DashMap concurrency

- Break monolithic records.rs into commands/, output/, parsing/ modules
- Add lib.rs with shared types (AppError, Car, BestCarRecord, etc.)
- Replace Arc<Mutex<HashMap>> with DashMap for concurrent access
- Add unified AppError enum with thiserror
- Add configurable CLI paths (--my-cars, --cars-db, --times-dir, --tracks-db)
- Add serde deserialization for Car struct
- Add CSV escaping for fields with commas/quotes/newlines
- Fix track name splitting: split_once -> rsplit_once for _a handling
- Add integration tests, proptest property-based tests, and unit tests
- Add rustfmt.toml configuration
- Update documentation (API, ARCHITECTURE, DATA_STRUCTURES, README)

src/commands/track.rs

@@ -0,0 +1,22 @@
+//! Track command implementation.
+//!
+//! Shows the best car for a specific track/condition/RQ combination.
+
+use top_drives::AppError;
+
+use crate::commands::{load_my_cars_or_warn, run_analysis};
+use crate::output::print_best_car;
+
+/// Executes the track command: shows best car for a specific track/condition/RQ.
+pub async fn run_track(
+    my_cars_path: &str,
+    cars_db_path: &str,
+    times_dir: &str,
+    track: &str,
+    condition: &str,
+    rq: u8,
+) -> Result<(), AppError> {
+    let my_data = load_my_cars_or_warn(my_cars_path)?;
+    let (ctx, _counts) = run_analysis(&my_data.owned, cars_db_path, times_dir).await?;
+    print_best_car(&ctx, track, condition, rq)
+}