[P3] the assetlinks guard couples the desktop and native build lanes to an Android file

scripts/verify-assetlinks.ts runs from verify:dist, which is also the tail of build:desktop and build:native. So an Android Digital Asset Links file now gates the Electron and iOS bundles: trim or relocate the public dir for a wrapper and those two lanes go red for a reason that has nothing to do with them.

The same coupling ships assetlinks.json and its certificate fingerprint inside both wrapper bundles, where nothing can ever fetch it.

Harmless today: the file is a few hundred bytes, carries no secret, and every lane keeps copyPublicDir on. The alternative costs something real, since teaching the guard which build mode it is running under adds a branch to the one script whose job is to be dumb and certain.

Flagged independently by two reviewers during the #798 review, so it is recorded rather than left to be rediscovered. Revisit when a wrapper build first needs a trimmed public dir.

Start with scripts/verify-assetlinks.ts and the verify:dist, build:desktop, and build:native entry points. Revisit this when a wrapper needs a trimmed public directory; done means Android assetlinks validation and packaging no longer gate or add the file to unrelated wrapper bundles.