fix: normalize uncharacterized read failures in the mock Studio gateway

`idempotent()` was fixed to wrap anything `work()` throws, with a documented
rationale: this port's contract is `StudioGatewayError` only, so nothing else
may cross it. Its `read()` sibling was left unwrapped, so an uncharacterized
internal failure on any of the seven read operations escaped as a raw `Error`
and reached UI code written to catch `StudioGatewayError`.

`read()` now applies the same `failureOf` classification. It has no
idempotency ledger, so only the problem half is used. `boundary()` stays
outside the wrap so an aborted request still surfaces as `AbortError`,
exactly as `idempotent()` arranges it -- asserted by the new test.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/features/tech-log/mock-studio-gateway.test.ts

@@ -639,3 +639,53 @@ test("getDocument's nextAction reflects the assembled WorkingCopyDetail, not a c
   assert.equal(edgeToken.currentValidation?.validatedVersion, 2);
   assert.equal(edgeToken.nextAction, "FIX_VALIDATION");
 });
+
+// Final fix wave, item 6. `idempotent()` normalizes anything `work()` throws
+// into a `StudioGatewayError` because that is the port's whole contract --
+// but its `read()` sibling did not, so an uncharacterized internal failure on
+// any of the seven read operations escaped the port as a raw `Error` and
+// reached UI code written to catch `StudioGatewayError`. An aborted request
+// must still surface as `AbortError`: `boundary()` runs outside the wrap, the
+// same way `idempotent()` already arranges it.
+test("read() normalizes an uncharacterized internal failure, and still lets an abort through", async () => {
+  let failing = false;
+  const gateway = createMockStudioGateway({
+    clock: { now: () => new Date(NOW) },
+    idGenerator: ids(),
+    dependencyRevision: {
+      current: () => {
+        if (failing) throw new Error("의존성 리비전을 읽지 못했습니다.");
+        return "catalog-2026-08-14";
+      },
+    },
+  });
+
+  const created = await gateway.createDocument(
+    emptyCase({ title: "읽기 경계", slug: "read-boundary", summary: "요약" }),
+    { idempotencyKey: "read-boundary-create" },
+  );
+
+  failing = true;
+  for (const [label, call] of [
+    ["getDocument", () => gateway.getDocument(created.id)],
+    ["getDashboard", () => gateway.getDashboard()],
+    ["listDocuments", () => gateway.listDocuments({})],
+  ] as const) {
+    await assert.rejects(call(), (error: unknown) => {
+      assert.ok(
+        isStudioGatewayError(error),
+        `${label}: expected a StudioGatewayError, got ${String(error)}`,
+      );
+      assert.equal(error.code, "STUDIO_UNAVAILABLE");
+      assert.equal(error.status, 500);
+      assert.equal(error.retryable, true);
+      return true;
+    });
+  }
+
+  const controller = new AbortController();
+  controller.abort();
+  await assert.rejects(gateway.getDocument(created.id, { signal: controller.signal }), {
+    name: "AbortError",
+  });
+});