Draw at Mac size, and build only for Apple Silicon

A Catalyst app draws its iPad interface at 77% unless it says otherwise,
so everything on the Mac was smaller than it should have been.
UIDesignRequiresCompatibility: false asks for the Mac idiom and true size.

ARCHS is pinned to arm64 for macOS: the default is a universal binary, and
the x86_64 half is weight nothing here will run. It was never running under
Rosetta -- the arm64 slice was always the one in use.

There is no zoom command. A pair was tried and taken out again: pageZoom
only works on a document that scrolls, and ipx's page is a fixed viewport
-- body is height:100dvh with overflow hidden -- which WebKit resolves
against the unzoomed window, so the page laid itself out at the wrong size
and was then scaled, spilling off the right edge with its toolbar clipped.
Text size belongs to the page, which owns its own layout.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ios/project.yml

@@ -34,6 +34,9 @@ targets:
         # works on a free personal team -- unlike CarPlay, which Apple has to grant.
         UIBackgroundModes: [audio]
         UILaunchScreen: {}
+        # Mac idiom rather than a scaled iPad. Without this a Catalyst app draws its iPad
+        # interface at 77%, which is why everything read small on the Mac.
+        UIDesignRequiresCompatibility: false
         # iOS 27 will not run an app that has not adopted the scene lifecycle. A CarPlay app is a
         # second scene beside this one, so its role goes here too when the entitlement exists.
         UIApplicationSceneManifest:
@@ -61,6 +64,9 @@ targets:
         # at all and the Mac destination simply did not exist.
         ASSETCATALOG_COMPILER_APPICON_NAME: AppIcon
         SUPPORTS_MACCATALYST: "YES"
+        # Apple Silicon only. The default builds a universal binary, and the x86_64 half is
+        # weight nothing here will ever run.
+        ARCHS[sdk=macosx*]: arm64
         DERIVE_MACCATALYST_PRODUCT_BUNDLE_IDENTIFIER: "NO"
 
   iPodderXUITests: