The clear-only-ours fix recorded the host's dir lazily, inside the rtl branch,
the first time it wrote. That is correct only while nothing else has written a
direction first. If anything set dir="rtl" on the host before that moment, the
element recorded rtl as "the page's own declaration" and then faithfully
restored it on every switch away from Arabic -- so the direction never cleared,
which is the defect this whole change exists to remove.
Measured on the Big Picture leaf: ar left rtl, and zh put rtl straight back,
while its three siblings with the same code passed. The difference was not the
code; it was that something writes rtl on that host before the element does.
Reading the attribute on the FIRST call instead, before any write of ours, is
the only moment it is certainly the page's and not ours. A page that genuinely
declares dir still owns that decision and still gets it back.
Five cases driven against the real function in all four files: no dir at boot,
a page declaring ltr, a page declaring rtl, an element mounting while already
Arabic, and -- the case that reproduces the failure -- a FOREIGN writer setting
rtl after mount and before ours. Restoring the lazy capture to one file fails
that fifth case alone and leaves the other four passing.
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