Custom font fallback no longer covers the whole BMP/SIP, so Segoe UI Emoji
can paint color glyphs again; CJK still prefers Noto Sans SC then YaHei.
Drop GaussianBlur compatible targets during BeginDraw (they retained GPU
memory as the candidate window grew), grow the composition swapchain in
64px steps without shrinking, and reuse Card chrome plus cached text
formats instead of reallocating them every layout.