What: build_update_products acquires npm inside the "Node dependencies" attempt and, whenever the
desktop product was requested but not built, prints `Desktop app build owed: <step> failed`.
posix.sh matches that line instead of the truncated follow-up text; windows.ps1 now projects it as
a manual outcome (it had no projection of the current follow-up at all).
Why: the 500-char follow-up leads with whichever product failed first, and an npm acquisition
failure escaped un-named, so a committed update whose Desktop was not rebuilt said "Update complete."
Red: pre-fix source_build.py -> test_unbuilt_desktop_is_named_on_one_whole_line[both] fail; pre-fix posix.sh -> truncated-followup hand-off test reports manual=false.
Green: test_source_build.py 15 passed; test_desktop_update_gateway_flag.py 3 passed. windows.ps1 needs a native run.
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