fix(imports): show a readable file format in the upload hint

The upload hint interpolated the raw `accept` string, so Trakt rendered
as "Upload a .json,.zip export…". Derive a label from `accept` with a new
locale-aware `formatList` helper ("JSON or ZIP"), and wrap the source
card descriptions in `msg` so they are translatable.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/i18n/test/format.test.ts

@@ -7,6 +7,7 @@ vi.mock("../src/index", () => ({
 import {
   formatBytes,
   formatDate,
+  formatList,
   formatNumber,
   formatRelativeTime,
   formatShortDate,
@@ -146,3 +147,17 @@ describe("formatBytes", () => {
     expect(formatBytes(1536 * 1024)).toBe("1.5 MB");
   });
 });
+
+describe("formatList", () => {
+  test("joins items as a conjunction by default", () => {
+    expect(formatList(["A", "B", "C"])).toBe("A, B, and C");
+  });
+
+  test("supports disjunctions", () => {
+    expect(formatList(["ZIP", "JSON"], { type: "disjunction" })).toBe("ZIP or JSON");
+  });
+
+  test("returns a single item unchanged", () => {
+    expect(formatList(["ZIP"], { type: "disjunction" })).toBe("ZIP");
+  });
+});