fix: respect vim.o.background when loading colorscheme

- Change default background.light from "ink" to "pearl" so light mode
    uses a light theme by default
  - Clear _EXPLICIT_THEME when load() is called without arguments so
    :colorscheme kanso properly respects vim.o.background setting

  Fixes #45

README.md

@@ -96,7 +96,7 @@ require('kanso').setup({
     end,
     background = {               -- map the value of 'background' option to a theme
         dark = "ink",           -- try "zen", "mist" or "pearl" !
-        light = "ink"           -- try "zen", "mist" or "pearl" !
+        light = "pearl"         -- try "zen", "mist" or "ink" !
     },
     foreground = "default",      -- "default" or "saturated" (can also be a table like background)
 })

lua/kanso/init.lua

@@ -25,7 +25,7 @@ M.config = {
         return {}
     end,
     ---@type { dark: string, light: string }
-    background = { dark = "ink", light = "ink" },
+    background = { dark = "ink", light = "pearl" },
     theme = "ink",
     ---@type { dark: "default"|"saturated", light: "default"|"saturated" }|"default"|"saturated"
     foreground = "default",
@@ -56,8 +56,11 @@ function M.load(theme)
     local utils = require("kanso.utils")
 
     -- If theme is explicitly provided, use it and disable background-based switching
+    -- If no theme is provided (e.g., :colorscheme kanso), clear explicit theme to respect vim.o.background
     if theme then
         M._EXPLICIT_THEME = theme
+    else
+        M._EXPLICIT_THEME = nil
     end
 
     -- Priority order for theme selection: