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/mod.rs

@@ -0,0 +1,63 @@
+//! Command dispatch and shared helpers.
+//!
+//! Provides the `run_analysis` orchestration function and `load_my_cars_or_warn`
+//! helper used by all command handlers.
+
+pub mod all;
+pub mod best;
+pub mod details;
+pub mod fetch;
+pub mod track;
+pub mod trash;
+pub mod wishlist;
+
+use std::collections::HashSet;
+use std::sync::Arc;
+
+use top_drives::{
+    AppError, AnalysisContext, CarCounts, MyCarsData,
+    compute_car_counts, load_my_cars_data,
+};
+
+use crate::parsing::parse_all_times;
+
+// ---------------------------------------------------------------------------
+// Helper: load my_cars.json with graceful degradation
+// ---------------------------------------------------------------------------
+
+/// Loads user car data, printing a warning and returning empty data if the file is missing.
+///
+/// Only `MissingFile` errors are gracefully degraded — parse errors and other
+/// failures are propagated to the caller, because running analysis with
+/// silently-corrupted ownership data would produce misleading results.
+pub fn load_my_cars_or_warn(path: &str) -> Result<MyCarsData, AppError> {
+    match load_my_cars_data(path) {
+        Ok(data) => Ok(data),
+        Err(AppError::MissingFile(msg)) => {
+            eprintln!("Warning: {msg}");
+            eprintln!("         Analysis will run without ownership data.");
+            Ok(MyCarsData::default())
+        }
+        Err(e) => Err(e),
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Analysis orchestration
+// ---------------------------------------------------------------------------
+
+/// Common analysis setup: loads user data, parses all timing files, and computes car counts.
+///
+/// Returns the analysis context (for stdout commands) and the aggregated car counts
+/// (for CSV output commands). The car list is stored inside `CarCounts`.
+pub async fn run_analysis(
+    owned: &HashSet<String>,
+    cars_db_path: &str,
+    times_dir: &str,
+) -> Result<(AnalysisContext, CarCounts), AppError> {
+    let ctx = AnalysisContext::new();
+    let owned = Arc::new(owned.clone());
+    let car_list = parse_all_times(owned, &ctx, cars_db_path, times_dir).await?;
+    let counts = compute_car_counts(&ctx, car_list)?;
+    Ok((ctx, counts))
+}