refactor: keep one full record per line

Each line of measurements/<emulator>.jsonl now holds the whole run:
every repetition, core logs, per-frame hashes and raw timings. The gzip
data files, the data schema and the split and join code are gone, and
core_probe --record appends one line. record_version moves to 3.

The seven records are rewritten once: each new line equals its old line
joined with its data file, and rebuilds the first-layout file its id
hashes.

website/src/components/MeasurementsExplorer.astro

@@ -52,7 +52,6 @@ const base = import.meta.env.BASE_URL.replace(/\/?$/, '/');
 		host: string;
 		runs: number;
 		record_url: string;
-		data_url: string;
 		sqlite: string;
 		core: { library: string; commit: string | null };
 	};
@@ -124,7 +123,7 @@ const base = import.meta.env.BASE_URL.replace(/\/?$/, '/');
 			host.append(text('span', item.host), text('small', `Core ${item.core.library}${item.core.commit ? ` at ${item.core.commit.slice(0, 12)}` : ''}`));
 			tr.append(host);
 			const record = document.createElement('td');
-			record.append(link(item.record_url, 'Record'), document.createTextNode(' '), link(item.data_url, 'data'));
+			record.append(link(item.record_url, 'Record'));
 			record.append(text('small', item.runs === 1 ? '1 run' : `${item.runs} runs`));
 			tr.append(record);
 			return tr;