retroarch-0002: core_info_database_supports_content_path O(C*(E+D)) per file
in ROM scanner, 193x speedup at C=100 cores; fix: ext->database hash map
built at core list init, O(1) lookups replace full core-list scan.
openemu-0001: SetupAssistant knownCores Array.contains O(N^2) core dedup,
17x op-count at N=35 cores; fix: Set<CoreDownload> for O(1) .contains.
MOADs 0002-0005 for both targets: RetroArch runloop is single-threaded by
design (no leaked context); no credential logging found (CHEEVOS_LOG_PASSWORD
guarded and undef'd by default); no unguarded cache thundering herd.
OpenEmu: no ThreadLocal patterns; no credential logging; NSCache is
thread-safe and duplicate fetch work is bounded.