Window Translucency shipped defaulting to Clear, which means the mode worth
finding is the one nobody sees — Glass is the better-looking half and the
reason the feature exists. A fresh macOS profile now starts with Glass
selected.
Nothing turns on. The intensity still defaults to 0, so the window is
byte-for-byte what it is today until the user moves the lever; the default
only decides which mode that lever will drive. windowOpacityFor stays 1 and
the window is still born with its opaque backing.
The one profile that must NOT flip is one already carrying a non-zero
intensity with no mode recorded: it predates the setting, has been rendering
as clear the whole time, and defaulting it to glass would change a window
someone deliberately tuned. normalizeMode takes the saved intensity and keeps
those on clear.
The renderer store was hand-rolling its own copy of this rule, so it now
routes through the shared normalizer and the two can't disagree.
The store's default test only passed because a beforeEach reset the atom
before it looked — it asserted the post-reset value, not the default, so it
would have stayed green through this change. It now snapshots the atom at
import time. All three mutations (default back to clear, escape hatch
removed, glass leaking onto non-mac) fail the suite.
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