Terminal drops Kitty graphics: libghostty-vt implements it, the web adapter never enables it

[nitrimandylis]

The embedded terminal drops Kitty graphics escapes, so anything that draws pixels shows nothing: timg, chafa -f kitty, yazi previews, imgcat, a TUI putting album art or a plot in the pane. The same commands work in Ghostty.

The protocol is already vendored. native/libghostty-vt/include/ghostty/vt/kitty_graphics.h has image storage and a placement iterator, and its header notes images are only stored once GHOSTTY_TERMINAL_OPT_KITTY_IMAGE_STORAGE_LIMIT is non-zero and a GHOSTTY_SYS_OPT_DECODE_PNG callback is installed. Neither symbol appears outside the headers, and apps/web/src/terminal/ghostty/README.md describes the renderer as backgrounds and style runs only. Mobile shares the ABI.

Would you take this? Happy to test a build.