4b95b757c6de  AX: isolated tree overcounts characters in a textarea after a dynamic edit that leaves a trailing line break

Classified as not security-relevant.
Triage note: Replaces isCollapsedTrailingLineBreak with offsetOfCollapsedTrailingNewline and lineRangeWithoutCollapsedTrailingNewline across AXTextMarker; an AX line-enumeration correctness refactor with no memory-safety bug and no attacker-relevant logic boundary.
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: smartptr_member_added (+6.47), bounds_guard (+4.32), null_guard (+2.59), large_churn (-2.0)