c3a249e70753f6bd2d4975fe6d96ea6612fb6a7d  [JSC] Use instance IDs for Wasm debugger virtual addresses

Classified as not security-relevant.
Triage note: Reworks the WebAssembly GDB-remote debugger (ENABLE(WEBASSEMBLY_DEBUGGER), Options::enableWasmDebugger) from module-keyed to instance-keyed addressing with siteCount breakpoint refcounting. Developer-only tooling not reachable from untrusted web content; fixes a breakpoint-lifetime issue in debug infrastructure, not a shipping vuln.
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), security_assert (+6.47), bounds_guard (+2.0), null_guard (+2.59), large_churn (-2.0)