docs: update documentation for normalized config and improve command

- Add improve command to all command tables and usage sections
- Add normalized_config field to BestCarRecord struct documentation
- Update CarCounts.by_rid type from String to (String, String)
- Update CarCounts.guid_to_rid type to HashMap<String, HashSet<(String, String)>>
- Add owned_configs field to MyCarsData and CarCounts docs
- Add normalize_to_final_build() to API docs
- Update CSV format examples to include FinalBuild column
- Update my_cars.json structure with engineMajor/weightMajor/chassisMajor
- Update timing file example with v2c_ version prefix
- Add version prefix stripping to data transformation docs
- Update CHANGELOG.md with Unreleased section
- Fix compare_records description to include normalized config sorting

docs/API.md

@@ -25,6 +25,7 @@ src/
 │   ├── wishlist.rs        # Wishlist command: wishlist.csv, add.csv, remove.csv
 │   ├── details.rs         # Details command: details.csv
 │   ├── track.rs           # Track command: stdout query
+│   ├── improve.rs         # Improve command: improve.csv (owned cars not at final build)
 │   └── all.rs             # All command: generates all output files
 ├── parsing/
 │   ├── mod.rs             # Core parsing: parse_car_times, update_best_car, parse_all_times
@@ -69,16 +70,17 @@ pub struct Car {
 ```rust
 #[derive(Debug, Clone)]
 pub struct BestCarRecord {
-    pub car_rid: String,    // Car identifier
-    pub brand: String,      // Manufacturer
-    pub only_name: String,  // Model name
-    pub year: u16,          // Year
-    pub rq: u8,             // RQ level
-    pub config: String,     // Tune config (111, 233, etc.)
-    pub time: f64,          // Track time in seconds
-    pub owned: bool,        // User ownership status
-    pub prize: bool,        // Prize car status
-    pub guid: String,       // Game identifier
+    pub car_rid: String,           // Car identifier
+    pub brand: String,             // Manufacturer
+    pub only_name: String,         // Model name
+    pub year: u16,                 // Year
+    pub rq: u8,                    // RQ level
+    pub config: String,            // Original tune config from JSON (111, 221, 233, etc.)
+    pub normalized_config: String, // Normalized final build (323, 233, or 332)
+    pub time: f64,                 // Track time in seconds
+    pub owned: bool,               // User ownership status
+    pub prize: bool,               // Prize car status
+    pub guid: String,              // Game identifier
 }
 ```
 
@@ -109,21 +111,25 @@ pub struct AnalysisContext {
 
 ```rust
 pub struct CarCounts {
-    pub by_rid: HashMap<String, (BestCarRecord, usize)>,
-    pub guid_to_rid: HashMap<String, String>,
+    pub by_rid: HashMap<(String, String), (BestCarRecord, usize)>,
+    pub guid_to_rid: HashMap<String, HashSet<(String, String)>>,
     pub car_map: HashMap<String, Car>,
     pub car_list: Vec<Car>,
+    pub owned_configs: HashMap<String, String>,
 }
 ```
 
+**Key grouping**: `by_rid` is keyed by `(car_rid, normalized_config)` so different tune configs of the same car are tracked separately. `guid_to_rid` maps each GUID to all `(rid, config)` pairs it appears under.
+
 #### `MyCarsData`
 **Parsed user data from `my_cars.json`**
 
 ```rust
 #[derive(Debug, Default)]
 pub struct MyCarsData {
-    pub owned: HashSet<String>,     // Owned car GUIDs
-    pub wishlist: HashSet<String>,  // Wishlist car GUIDs
+    pub owned: HashSet<String>,                  // Owned car GUIDs
+    pub wishlist: HashSet<String>,               // Wishlist car GUIDs
+    pub owned_configs: HashMap<String, String>,  // GUID → actual tune config (e.g., "233")
 }
 ```
 
@@ -183,11 +189,12 @@ pub enum AppError {
 
 - Sorts by: RQ → Brand → Model name
 
-#### `compute_car_counts(ctx: &AnalysisContext, car_list: Vec<Car>) -> CarCounts`
+#### `compute_car_counts(ctx: &AnalysisContext, car_list: Vec<Car>, owned_configs: HashMap<String, String>) -> CarCounts`
 **Aggregates per-car win counts from analysis context**
 
 - Iterates all entries in the `DashMap`
-- Returns `CarCounts` with by_rid, guid_to_rid, car_map, and car_list
+- Groups by `(car_rid, normalized_config)` for per-config tracking
+- Returns `CarCounts` with by_rid, guid_to_rid, car_map, car_list, and owned_configs
 
 #### `escape_csv_field(field: &str) -> String`
 **Escapes a field for safe CSV inclusion**
@@ -195,6 +202,14 @@ pub enum AppError {
 - Wraps in quotes if field contains comma, quote, newline, or carriage return
 - Doubles internal quotes per CSV spec
 
+#### `normalize_to_final_build(config: &str) -> String`
+**Normalizes a tune configuration to the closest "final build"**
+
+- The three final builds are `"323"`, `"233"`, and `"332"` (permutations of digits summing to 8)
+- For non-standard configs, repeatedly increments the smallest digit until sum reaches 8
+- Returns the original string unchanged if config cannot be parsed or sum already ≥ 8
+- Version prefixes (`v2c_`, `v1c_`) are stripped at parse time before reaching this function
+
 ---
 
 ## Records Binary (`src/records.rs`)
@@ -221,6 +236,7 @@ CLI entry point. Defines command-line arguments and dispatches to command handle
 | `all` | Generate all output files in a single pass | `--min-count N`, `--max-wishlist M` |
 | `details` | Generate `details.csv` with all timing data | None |
 | `track` | Show best car for specific track/condition/RQ | `<track> <condition> <rq>` |
+| `improve` | Generate `improve.csv` (owned cars not at final build) | None |
 
 ---
 
@@ -309,7 +325,7 @@ Loads car database, parses all timing files concurrently, and computes car count
 #### `write_best_csv(counts)`, `write_very_best_csv(counts, min_count)`
 **Generate best car CSV files**
 
-- Format: `RQ,Brand,Model,Year,Count`
+- Format: `RQ,Brand,Model,Year,FinalBuild,Count`
 - Fields are CSV-escaped
 
 #### `write_trash_csv(counts, owned)`
@@ -323,7 +339,16 @@ Loads car database, parses all timing files concurrently, and computes car count
 
 - Computes ideal wishlist once
 - Derives all three files from it
-- Format: `RQ,Brand,Model,Year,Count`
+- Format: `RQ,Brand,Model,Year,FinalBuild,Count`
+
+#### `write_improve_csv(counts) -> Result<usize, AppError>`
+**Generate improve CSV file**
+
+- Lists owned cars whose actual player config is not yet a final build (323/233/332)
+- Uses actual player config from `my_cars.json`, not timing data configs
+- Format: `RQ,Brand,Model,Year,Target,Count`
+- Sorted by track count descending (most impactful upgrades first)
+- Returns the number of cars written
 
 #### `write_details_csv(ctx)`
 **Generate comprehensive timing data CSV**
@@ -347,4 +372,4 @@ Loads car database, parses all timing files concurrently, and computes car count
 #### `compare_records(a: &BestCarRecord, b: &BestCarRecord) -> std::cmp::Ordering`
 **Comparison for BestCarRecord sorting**
 
-- Sorts by: RQ → Brand → Model name
+- Sorts by: RQ → Normalized Config → Brand → Model name