12c9964c288d8b300efadf31272995b492622022  Address Safer C++ static analysis warnings in WebCore bindings code

Classified as not security-relevant.
Triage note: Large SaferCPP sweep across bindings/js (CheckedPtr/RefPtr/protect, SaferCPPExpectations removals) plus a builtins generator tweak. Proactive hardening/refactor, no concrete attacker-reachable bug fixed.
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), null_guard (+1.2), uaf_lifetime (+3.57), msg_noise (-2.5), area:Source/WebCore/dom (+2.0), large_churn (-2.0)