848538f2e9b5f3d03e6ec8484b752ce6433ff132  [IFC] text-overflow truncates a unicode-bidi: plaintext line in the wrong direction

Classified as not security-relevant.
Triage note: truncate()/truncateOverflowingDisplayBoxes() now take an explicit isLeftToRightInlineDirection flag sourced from displayLine.isLeftToRightInlineDirection() instead of deriving direction from rootStyle.writingMode(). An RTL ellipsis/truncation direction correctness refactor; no security impact.
This commit was flagged by the signal scorer and reviewed by AI (not a human). It is listed only so the triage is auditable; there is no root-cause analysis because this is not a vulnerability fix.

Structural signals: null_guard (+1.2), clamp_saturate (+2.92), msg_medium (+2.0), msg_soft (+1.0), msg_noise (-2.5), area:Source/WebCore/layout (+2.0), surgical (+1.3)