ca158eb19b753004c61c9405265669ccfdd8557a  [JSC] Adopt the instance-scoped qWasmGlobal packet form

Classified as not security-relevant.
Triage note: Predominantly a feature in the WEBASSEMBLY_DEBUGGER component: adds soleInstanceOfModule, instanceForModule/instanceForFrame, qWasmInstance qSupported advertisement, README docs and new tests. The only hardening is switching parseDecimal to parseInteger<uint32_t> to reject non-numeric frame/global fields, which is debug-only and not attacker-reachable in normal browsing.
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 (+3.0), security_assert (+6.47), null_guard (+2.59), clamp_saturate (+1.8), large_churn (-2.0)