feat(worker): ranged 7z listing orchestrator + RangeReader

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

worker/src/archive/ranged/sevenz-ranged.test.ts

@@ -28,3 +28,38 @@ describe("parseSevenZSignatureHeader", () => {
     expect(parseSevenZSignatureHeader(MAGIC)).toBeNull();
   });
 });
+
+import { readSevenZListingRanged } from "./sevenz-ranged.js";
+import type { RangeReader } from "./range-reader.js";
+
+describe("readSevenZListingRanged", () => {
+  it("reads the signature + end-header regions and reconstructs for 7z l", async () => {
+    const size = 5_000_000;
+    const endHeaderOffset = 4_900_000; // absolute
+    const nextHeaderOffset = endHeaderOffset - 32;
+    const sig = Buffer.alloc(32);
+    Buffer.from([0x37, 0x7a, 0xbc, 0xaf, 0x27, 0x1c]).copy(sig, 0);
+    sig.writeBigUInt64LE(BigInt(nextHeaderOffset), 12);
+    sig.writeBigUInt64LE(100n, 20);
+
+    const reads: { offset: number; length: number }[] = [];
+    const read: RangeReader = async (_id, offset, length) => {
+      reads.push({ offset, length });
+      if (offset === 0) return sig.subarray(0, length);
+      return Buffer.alloc(length, 0xAB); // stand-in end-header bytes
+    };
+
+    // Inject a fake lister via the module boundary: readSevenZListingRanged
+    // calls listFromSparse(parts, read7zContents). We assert the ranged reads
+    // it issued; the sparse file + real 7z is covered by live verification.
+    const entries = await readSevenZListingRanged(
+      [{ fileId: "1", fileSize: BigInt(size), fileName: "a.7z" }],
+      read,
+    );
+    // entries may be null here because the stand-in bytes aren't a real 7z;
+    // the contract under test is the ranged-read offsets:
+    expect(reads[0]).toEqual({ offset: 0, length: 32 });
+    expect(reads[1]).toEqual({ offset: endHeaderOffset, length: 100 });
+    expect(entries === null || Array.isArray(entries)).toBe(true);
+  });
+});