Recreate the main swap chain when only its flags change on reset. (#3986)

Context::reset moves the per-surface flags (MSAA, sRGB, HiDPI) off the reset flags onto SwapChain::flags, but every backend's updateResolution gate still compared only the stripped reset flags, so a runtime MSAA change was dropped.
(cherry picked from commit 1ffb270f91a63403c069fcf652bd2411d962b437)

src/renderer_webgpu.cpp

@@ -2696,6 +2696,7 @@ WGPU_IMPORT
 			||  m_mainSwapChain.height             != _swapChain.height
 			||  m_mainSwapChain.nwh                != _swapChain.nwh
 			||  m_mainSwapChain.ndt                != _swapChain.ndt
+			||  m_mainSwapChain.flags              != _swapChain.flags
 			||  m_reset              != flags
 				)
 			{