Background fit modes: host renders

Evidence class: host render (headless Cairo/image pixels from the production placement code). Not a QEMU run, not a native grim capture and not a panel photograph; task 3.2 of openspec/changes/the-background-chooser-supports-fill-solid-and-video stays open until the same five modes are captured on the board.

Base revision: 0785fc711838 (master), candidate: the commit that adds this directory on branch bg-fill-solid.

Sources (pinned built-in themes, omacom/omarchy revision 28ceaae70ebac3a0edcc21f2faa77a90dc6d404c, as packaged by nix/handheld-theme-default; see ../bundled-backgrounds-host.md):

Theme	Mode	Source image	`background` role
`catppuccin`	dark	`backgrounds/2-waves.webp` (landscape)	`#1e1e2e`
`catppuccin-latte`	light	`backgrounds/1-color-fade.webp` (1536x1024)	`#eff1f5`

Command (from the repository root, host cargo, store path of the packaged default):

T=/nix/store/1aq21qmfshf527fy6r62h39crfkpi1px-handheld-theme-default-28ceaae7/share/omarchy/themes
cargo run --offline --manifest-path nix/rust-shell-client/Cargo.toml \
  --example render_background_fit_evidence -- \
  docs/evidence/omarchy-themes/background-fit-modes-host \
  dark-catppuccin $T/catppuccin/backgrounds/2-waves.webp '#1e1e2e' \
  light-catppuccin-latte $T/catppuccin-latte/backgrounds/1-color-fade.webp '#eff1f5'

Each PNG is 284x616 (the 568x1232 panel at half size, to keep committed bytes small; the placement is scale-invariant). The harness writes a generation report.json carrying fit_mode and the palette’s background, reads it with appearance::generation_wallpaper_fit (the function the shell uses) and renders through BackgroundCache::render, so the colour and mode come through the real resolution path.

What each image shows for a landscape source on a portrait canvas:

crop: aspect-preserving cover, centred; the sides are trimmed.
fit: aspect-preserving, whole image visible, black bars above and below (the pre-existing letterbox colour).
center: native pixels, centred, no scaling; black outside the source.
fill: stretched to the full canvas, no bars and no crop; the picture is distorted (new in this change).
solid: no image at all, the theme’s own background role (new in this change).

Limits: panel colour, gamma and AMOLED appearance are not represented; no touch interaction, no chooser rendering and no helper round trip is exercised here. The chooser control (tapping the “Backgrounds” heading) is covered by theme_ui unit tests only.