Handle no-record cars and per-copy trash listing

Empty API responses (200 + empty body) mean "known car, no times
submitted yet" on the records site — typically newly released prize
cars. Previously each such car burned 3 retries with backoff and then
aborted the entire fetch; 27 cars in the current DB hit this.

- Add AppError::EmptyResponse { url } as a distinct, deterministic
  failure class; get_file fails immediately instead of retrying
- fetch_car downgrades EmptyResponse to a skip with an info log, so
  fetch completes; the next fetch picks the cars up automatically
  once records exist
- parse_car_times treats empty (or whitespace-only) timing files
  like missing files, eliminating "EOF while parsing a value at line
  1 column 0" parse errors from stale empty files

trash.csv Config column now lists only the copies to delete: for a
car whose one tune is a final build not best on any track (e.g.
owned 332 next to a best-on-213-tracks 323), only the dead tune is
shown instead of joining all owned configs. Categories 1 and 3 still
list all configs since the whole car goes.

Tests: empty response makes exactly 1 request and yields the
EmptyResponse variant; empty file parses Ok; partial-copy trash
shows only the deletable config.

CHANGELOG.md

@@ -32,6 +32,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 - `plans/code-review-v2.md` (completed action items)
 
+### Fixed
+- `trash.csv` Config column now lists only the copies to delete: for cars where just one tune is useless (e.g. owned 332 + best-everywhere 323) only the dead tune is shown instead of all owned configs
+- Cars the records site knows but has no times for (typically new prize cars, returned as `200` with an empty body) no longer abort `fetch` after 3 retries — they are skipped with an info log
+- Empty timing files are now treated like missing files instead of producing `EOF while parsing a value` parse errors
+
 ## [0.3.0] - 2026-05-07
 
 ### Added