After detection failed, Add Source stayed enabled and tapping it just
re-ran detection into the same error — an enabled-looking button that
visibly did nothing, forever (TV8). The error state now shows the
button that can help, Retry Detection, holds a perceptible detecting
beat even when the host fails instantly, and hides the display-name
section that made the form read as submittable. Add Source itself now
requires a detected type, so it can no longer render enabled without
one.