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58f8029264
Replace copy-assignment with raw memcpy in the WiFi scan result insertion sort. Copy assignment on WiFiScanResult calls CompactString's destructor then placement-new for every shift, which means delete[]/new[] per shift for heap-allocated SSIDs. With 70+ networks visible (e.g., during captive portal transition showing full scan results), this caused event loop blocking from hundreds of heap allocations in a tight loop on an 80MHz ESP8266. This optimization is safe because we're permuting elements within the same array - each slot is overwritten exactly once, so no ownership duplication occurs. CompactString stores either inline data or a heap pointer, never a self-referential pointer (unlike libstdc++ std::string SSO). This was made possible by PR#13472 which replaced std::string with CompactString. Static asserts guard the memcpy safety assumptions at compile time. Confirmed on real device: event loop blocking during captive portal transition is eliminated and WiFi connection is slightly faster.
