feat(my-videos): bucket object listing for reconciliation (Phase 2, step 2)

Adds the bucket-enumeration primitive the My Videos tab needs to find orphan and
missing files:
- s3 layer: ListObjectsV2Command wired into the SDK wrapper + a paginated
  listObjects({ s3, bucket, prefix, maxKeys }) helper (follows continuation
  tokens, bounded by maxKeys).
- r2Service.listVideoStorageObjects({ npub|pubkey }) — unlock-gated, lists under
  the user's own u/<npub>/ prefix; returns { ok, reason, keys }. Body lives in
  r2ServiceHelpers (with a shared buildProviderClient) so r2Service stays under
  its file-size budget; ensureS3SdkLoaded is injectable via ctx for testing.

Tests + mutation-verified: never lists while locked (storage-locked, no call),
no-connection / missing-bucket gating, and unlocked listing is scoped to the
user's own u/<npub>/ prefix (empty-prefix mutation fails). Removing the lock gate
or widening the prefix each fail a scenario.

Build + full lint green (r2Service back under limit).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

tests/my-videos-list-objects.test.mjs

@@ -0,0 +1,83 @@
+// listVideoStorageObjects backs the My Videos tab's bucket reconciliation. It is
+// UNLOCK-GATED — it must never attempt a bucket listing without credentials —
+// and when unlocked it must list under the user's own prefix (u/<npub>/) so it
+// can't enumerate (or later act on) anything outside the user's space.
+
+import "./test-helpers/setup-localstorage.mjs";
+import assert from "node:assert/strict";
+import test from "node:test";
+import { listVideoStorageObjects } from "../js/services/r2ServiceHelpers.js";
+
+const NPUB = "npub1exampleexampleexample";
+
+function makeCtx(overrides = {}) {
+  const calls = { listObjects: [] };
+  const ctx = {
+    resolveConnection: async () => null,
+    ensureS3SdkLoaded: async () => {},
+    makeR2Client: () => ({}),
+    makeS3Client: () => ({}),
+    listObjects: async (args) => {
+      calls.listObjects.push(args);
+      return ["u/npub1example/a/v.mp4", "u/npub1example/b/v.mp4"];
+    },
+    ...overrides,
+  };
+  return { ctx, calls };
+}
+
+const UNLOCKED = {
+  provider: "cloudflare_r2",
+  accountId: "acc",
+  bucket: "bkt",
+  accessKeyId: "AK",
+  secretAccessKey: "SK",
+};
+
+test("locked storage never lists (returns storage-locked)", async () => {
+  const { ctx, calls } = makeCtx();
+  const result = await listVideoStorageObjects(ctx, {
+    npub: NPUB,
+    credentials: { ...UNLOCKED, accessKeyId: "", secretAccessKey: "" },
+  });
+  assert.equal(result.ok, false);
+  assert.equal(result.reason, "storage-locked");
+  assert.equal(calls.listObjects.length, 0, "must not attempt a listing while locked");
+});
+
+test("no resolvable connection returns no-connection", async () => {
+  const { ctx, calls } = makeCtx();
+  const result = await listVideoStorageObjects(ctx, { npub: NPUB });
+  assert.equal(result.reason, "no-connection");
+  assert.equal(calls.listObjects.length, 0);
+});
+
+test("missing bucket is reported and not listed", async () => {
+  const { ctx, calls } = makeCtx();
+  const result = await listVideoStorageObjects(ctx, {
+    npub: NPUB,
+    credentials: { ...UNLOCKED, bucket: "" },
+  });
+  assert.equal(result.reason, "missing-bucket");
+  assert.equal(calls.listObjects.length, 0);
+});
+
+test("unlocked storage lists under the user's own u/<npub>/ prefix", async () => {
+  const { ctx, calls } = makeCtx();
+  const result = await listVideoStorageObjects(ctx, {
+    npub: NPUB,
+    credentials: UNLOCKED,
+  });
+  assert.equal(result.ok, true);
+  assert.equal(calls.listObjects.length, 1);
+  assert.equal(
+    calls.listObjects[0].prefix,
+    `u/${NPUB}/`,
+    "must scope the listing to the user's own prefix",
+  );
+  assert.equal(calls.listObjects[0].bucket, "bkt");
+  assert.deepEqual(result.keys, [
+    "u/npub1example/a/v.mp4",
+    "u/npub1example/b/v.mp4",
+  ]);
+});