2ea91a8354
The three "plain desktop browser" export tests (the PNG and GCG downloads plus the legacy-Telegram clipboard copy) assumed navigator.share is absent — true for Chromium and for WebKit on the Linux CI host, but desktop WebKit on macOS exposes a working Web Share API. There shareUrlAsFile / pickGcgDelivery take the share branch, so no download event fires and the "GCG copied to the clipboard" toast never shows, and the tests failed only on macOS WebKit. Pin navigator.share/canShare off in those three tests (a withoutWebShare helper that mirrors the inverse stub the share-sheet test already uses), so the delivery path under test is deterministic and identical across engines and OSes. Test-only; no production change. Full e2e suite: 228 passed on Chromium + WebKit.