chore(palettes): remove dead per-palette files

Two clusters of palette-tree dead surface:

(1) themes/palettes/{flexoki-light,lumon,retro-82,rose-pine}/apps/
chromium.theme — 9-byte comma-separated RGB strings that no script
or Nix module reads. Chromium theming is driven by managed policies
in core/system/browser.nix (BrowserThemeColor / BrowserColorScheme
derived from the active palette's base00 + light-mode flag), not by
per-palette files. The chromium.theme files were vestigial from an
earlier chromium-theming mechanism.

(2) themes/palettes/summer-day/apps/kitty/{kitty.conf,everforest-
light.conf} — a 76KB stray kitty config in a nested apps/kitty/
subdirectory. features/apps/kitty/config/kitty.conf includes
~/.config/nomarchy/current/theme/kitty.conf (root of theme dir, not
under apps/), and themes/engine/files.nix now generates that file
from the active palette's base16 colors (commit 8d3ce2d). So the
summer-day file was at the wrong path AND superseded by the
generator.

`nix flake check --no-build` passes.

themes/palettes/flexoki-light/apps/chromium.theme

@@ -1 +0,0 @@
-242,240,229

themes/palettes/lumon/apps/chromium.theme

@@ -1 +0,0 @@
-14,31,41

themes/palettes/retro-82/apps/chromium.theme

@@ -1 +0,0 @@
-0,23,46

themes/palettes/rose-pine/apps/chromium.theme

@@ -1 +0,0 @@
-210,196,219

themes/palettes/summer-day/apps/kitty/everforest-light.conf

@@ -1,44 +0,0 @@
-# A port of forest night by sainnhe
-# https://github.com/sainnhe/forest-night
-
-font_family JetBrainsMono Nerd Font
-font_size 12.0
-
-foreground            #323d43
-background            #fdf6e3
-selection_foreground  #e4e1cd
-selection_background  #d3dbc8
-url_color             #415c6d
-cursor                #7fbbb3
-
-# black
-color0   #4a555b
-color8   #525c62
-
-# red
-color1   #e68183
-color9   #e68183
-
-# green
-color2   #a7c080
-color10  #a7c080
-
-# yellow
-color3   #dbbc7f
-color11  #dbbc7f
-
-# blue
-color4  #7fbbb3
-color12 #7fbbb3
-
-# magenta
-color5   #d699b6
-color13  #d699b6
-
-# cyan
-color6   #83c092
-color14  #83c092
-
-# white
-color7   #f3efda
-color15  #f3efda