feat(themes): port legacy rofi identities for summer-day/night

themes/<slug>/rofi.rasi whole-swaps for the two themes that had a
distinct launcher look in the legacy branch — inverted window (bg=fg),
green inputbar, yellow bottom-border accent, rounded. Adapted: dropped
the configuration{} block (rofi.nix owns modi/terminal/show-icons) and
swapped the unshipped Iosevka 17 for a shipped Nerd Font.

Verified: both .rasi parse under `rofi -dump-theme`; the whole-swap
selects per active theme (summer-night → #2d353b/#a7c080, summer-day →
#fdf6e3, others → the generated palette theme); flake check green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -288,10 +288,10 @@ close · `SUPER+1..9` workspaces · `Print` region screenshot.
   palette recolors and already match. Remaining: a visual pass over all
   six on the live ISO
 - **Per-theme rofi identity:** the `themes/<slug>/rofi.rasi` whole-swap
-  mechanism ships; what remains is porting the legacy `rofi.rasi` designs
-  (summer-day/night already have them in the legacy branch) for the
-  identity themes — rofi's `.rasi` expresses their per-element looks
-  (green inputbar, inverted window) directly, unlike the old flat scheme
+  ships, and summer-day/night carry their legacy designs (inverted window,
+  green inputbar, yellow bottom-border). Remaining: author `.rasi`
+  identities for the other four ported themes if/when they want one (the
+  generated palette theme is the default and looks fine)
 - **Faster switches:** move `backgrounds/` out of the flake source (the 86 MB
   re-copy on every state write is the main eval tax), then pre-built theme
   variants if still needed