Move release manifest into lib/ to fix dependency direction

Architecture review (hai-architecture / APoSD) of the shipped redesign found one
structural smell: the shared lib/ layer imported the release manifest from
components/ — data in the presentation layer, dependency pointing the wrong way.
- move components/release-links.generated.ts -> lib/; update the four importers
  and the README. lib/ no longer imports from components/.
- downloads.ts: reuse PlatformDownload["id"] instead of re-declaring the union.

No behavior change (download counter + tracked hrefs identical); build + e2e 12/12.

landing/components/sections/download-section.tsx

@@ -5,7 +5,7 @@ import { Download } from "reicon-react/icons/Download";
 import { Container } from "../ui/container";
 import { Reveal } from "../ui/reveal";
 import { SectionHeading } from "../ui/section-heading";
-import { platformDownloads, releaseVersion } from "../release-links.generated";
+import { platformDownloads, releaseVersion } from "../../lib/release-links.generated";
 import { DOWNLOAD_COUNT_SEED, getTrackedDownloadHref } from "../../lib/downloads";
 
 export function DownloadSection() {