feat: formatResultSummary shows L1/L2 cache hit rates

Display per-DO (L1) and per-datacenter (L2) page cache hit rates
in the one-line summary. Complements the merge telemetry fix that
now propagates cacheHits/cacheMisses/edgeCacheHits/edgeCacheMisses
from fragment DOs through the merge layer.

Example: "20 rows in 3.2ms | L1: 8/10 hits | L2: 3/10 hits"

Author: teamchong

src/format.test.ts

@@ -94,6 +94,28 @@ describe("formatResultSummary", () => {
     expect(summary).toContain("meta: 2.0ms");
   });
 
+  it("includes L1 and L2 cache hit rates", () => {
+    const result: QueryResult = {
+      rows: [{}], rowCount: 1, columns: ["a"],
+      bytesRead: 1000, pagesSkipped: 0, durationMs: 5.0,
+      cacheHits: 8, cacheMisses: 2,
+      edgeCacheHits: 3, edgeCacheMisses: 7,
+    };
+    const summary = formatResultSummary(result);
+    expect(summary).toContain("L1: 8/10 hits");
+    expect(summary).toContain("L2: 3/10 hits");
+  });
+
+  it("omits cache stats when zero", () => {
+    const result: QueryResult = {
+      rows: [{}], rowCount: 1, columns: ["a"],
+      bytesRead: 0, pagesSkipped: 0, durationMs: 1.0,
+    };
+    const summary = formatResultSummary(result);
+    expect(summary).not.toContain("L1:");
+    expect(summary).not.toContain("L2:");
+  });
+
   it("singular row", () => {
     const result: QueryResult = {
       rows: [{}],

src/format.ts

@@ -57,6 +57,14 @@ export function formatResultSummary(result: QueryResult & Partial<LocalTimingInf
     parts.push(`wasm: ${result.wasmExecMs.toFixed(1)}ms`);
   }
 
+  if ((result.cacheHits ?? 0) + (result.cacheMisses ?? 0) > 0) {
+    parts.push(`L1: ${result.cacheHits ?? 0}/${(result.cacheHits ?? 0) + (result.cacheMisses ?? 0)} hits`);
+  }
+
+  if ((result.edgeCacheHits ?? 0) + (result.edgeCacheMisses ?? 0) > 0) {
+    parts.push(`L2: ${result.edgeCacheHits ?? 0}/${(result.edgeCacheHits ?? 0) + (result.edgeCacheMisses ?? 0)} hits`);
+  }
+
   if (result.spillBytesWritten && result.spillBytesWritten > 0) {
     parts.push(`${formatBytes(result.spillBytesWritten)} spilled`);
   }