fix: Lance broadcast totalRows, Iceberg bench discovery, add conformance tests

- Master DO now includes totalRows and r2Prefix in broadcast payload
- Query DO uses broadcast totalRows for Lance (was computing 0 from columns)
- Query DO lazy-loads full dataset when r2Prefix present in broadcast
- Bench script triggers Iceberg lazy-load via query before benchmarking
- Add 66 conformance tests: Parquet/Lance parsing, column decoding,
  page skipping, filter correctness, cross-format consistency

Author: teamchong

scripts/bench.ts

@@ -167,6 +167,7 @@ async function main(): Promise<void> {
     "simple.parquet", "simple_plain.parquet", "simple_snappy.parquet",
     "benchmark_100k.parquet", "benchmark_100k_uncompressed.parquet",
     "bench_100k_3col.parquet", "bench_100k_numeric.parquet", "bench_1m_numeric.parquet",
+    "bench_iceberg_100k",
   ];
 
   console.log("Refreshing tables...");
@@ -189,6 +190,27 @@ async function main(): Promise<void> {
   }
   await new Promise(r => setTimeout(r, 500));
 
+  // Pre-register Iceberg tables by triggering lazy-load via a query
+  const icebergTables = ["bench_iceberg_100k"];
+  for (const tbl of icebergTables) {
+    try {
+      const resp = await fetch(`${BASE_URL}/query`, {
+        method: "POST",
+        headers: { "content-type": "application/json" },
+        body: JSON.stringify({ table: tbl, filters: [], projections: ["id"], limit: 1 }),
+      });
+      if (resp.ok) {
+        console.log(`  Iceberg OK: ${tbl}`);
+      } else {
+        const text = await resp.text();
+        console.log(`  Iceberg Skip: ${tbl} (${resp.status}: ${text.slice(0, 100)})`);
+      }
+    } catch {
+      console.log(`  Iceberg Skip: ${tbl}`);
+    }
+  }
+  await new Promise(r => setTimeout(r, 500));
+
   const tablesResp = await fetch(`${BASE_URL}/tables`);
   const { tables } = await tablesResp.json() as { tables: { name: string; totalRows: number }[] };
   console.log("\nAvailable tables:", tables.map(t => `${t.name}(${t.totalRows})`).join(", "));