nook: say macOS 14.2, which is what the app actually needs

The landing page, the FAQ and the downloads list still promised macOS 14. The
app cannot start there: dyld refuses it on 14.0 and 14.1 because a
CoreAudio overlay symbol its mixer uses only exists from 14.2, and the old
floor in its bundle had LaunchServices launching it on machines that could
never run it (NOOK-881).

The FAQ answer named the observation framework as the reason for 14; the
binding reason is the per-app audio tap API, which Apple shipped in 14.2. The
downloads list said 14.6+, which was already stricter than the truth.

InputHalo and Gaze still read 14.6+; their floors are their own and this
change leaves them alone.

Tests: bun test src/routes/nook (2 pass); bunx tsc --noEmit reports nothing in
the three files changed (the checkout's 286 pre-existing errors are elsewhere).

NOOK-881

src/routes/downloads.tsx

@@ -110,7 +110,7 @@ function MainDownloadsPage() {
 
               <div class="flex flex-col items-center gap-3">
                 <span class="text-subtext0 font-mono text-sm">
-                  platform: macOS (14.6+)
+                  platform: macOS (14.2+)
                 </span>
                 <Button
                   variant="download"