cars: default to most-common-in-NL order; dex numbers oldest first with unknown years last (--renumber)

scripts/cars-import.ts

@@ -4,6 +4,7 @@
 //   bun scripts/cars-import.ts --dry-run             fetch + build only, print a summary
 //   bun scripts/cars-import.ts --cache /tmp/cars     reuse raw downloads from that folder
 //   bun scripts/cars-import.ts --dry-run --out x.json   also dump the built catalogue
+//   bun scripts/cars-import.ts --renumber           reassign Dex numbers from #1 (oldest first)
 //
 // Sources (no API keys):
 //  - fueleconomy.gov vehicles.csv: every US EPA-tested car since 1984 (make, base model,
@@ -26,6 +27,8 @@ import { join } from 'node:path';
 
 const args = process.argv.slice(2);
 const dryRun = args.includes('--dry-run');
+// --renumber: hand out Dex numbers from #1 again instead of keeping existing ones.
+const renumber = args.includes('--renumber');
 const cacheDir = args.includes('--cache') ? args[args.indexOf('--cache') + 1] : null;
 const outFile = args.includes('--out') ? args[args.indexOf('--out') + 1] : null;
 
@@ -927,12 +930,12 @@ async function write(brands: ReturnType<typeof build>) {
 			const existing = await tx<{ id: number; dex: number; brand_id: number; slug: string }[]>`
 				select id, dex, brand_id, slug from cars.models`;
 			const byKey = new Map(existing.map((e) => [`${e.brand_id}|${e.slug}`, e]));
-			let nextDex = Math.max(0, ...existing.map((e) => e.dex)) + 1;
+			let nextDex = renumber ? 1 : Math.max(0, ...existing.map((e) => e.dex)) + 1;
 			const all = brands
 				.flatMap((b) => b.models.map((m) => ({ b, m, brandId: brandIds.get(b.slug)! })))
 				.sort(
 					(x, y) =>
-						x.m.firstYear - y.m.firstYear ||
+						(x.m.firstYear ?? 9999) - (y.m.firstYear ?? 9999) ||
 						x.b.name.localeCompare(y.b.name) ||
 						x.m.name.localeCompare(y.m.name)
 				);
@@ -942,7 +945,7 @@ async function write(brands: ReturnType<typeof build>) {
 			await tx`delete from cars.variants`;
 			let variantCount = 0;
 			for (const { m, brandId } of all) {
-				const prev = byKey.get(`${brandId}|${m.slug}`);
+				const prev = renumber ? undefined : byKey.get(`${brandId}|${m.slug}`);
 				const dex = prev?.dex ?? nextDex++;
 				const { variants, ...cols } = m;
 				const row = {