fix!: remove auto-apply from setup() to match standard convention

BREAKING CHANGE: setup() no longer automatically applies the theme.
Users must now call vim.cmd.colorscheme('oasis') after setup().

This aligns Oasis with the standard pattern used by other popular
colorscheme plugins (Catppuccin, Tokyonight, etc.) where setup()
only configures and :colorscheme applies the theme.

Updated all documentation examples to show the two-step pattern:
- Installation section
- Auto-switching configuration
- Palette overrides
- Highlight overrides
- Usage section with clearer headers

Fixes the issue where setup() would override explicit colorscheme
choices, preventing users from configuring Oasis features (like
auto-switching) without forcing it as their active colorscheme.

Author: uhs-robert

README.md

@@ -150,6 +150,7 @@ Install the theme with your preferred package manager, such as
     require('oasis').setup({
       style = "lagoon",  -- Optional: Choose any style like `lagoon` or 'dune'.
     })
+    vim.cmd.colorscheme('oasis')  -- Apply the theme
   end
 }
 ```
@@ -196,6 +197,7 @@ require('oasis').setup({
   dark_style = "lagoon",  -- Style when background is dark
   light_style = "dawn"      -- Style when background is light
 })
+vim.cmd.colorscheme('oasis')  -- Apply the theme
 ```
 
 </details>
@@ -236,6 +238,7 @@ require('oasis').setup({
     }
   }
 })
+vim.cmd.colorscheme('oasis')  -- Apply the theme
 ```
 
 </details>
@@ -254,23 +257,34 @@ require('oasis').setup({
     Identifier = "Function"  -- Link to another group
   }
 })
+vim.cmd.colorscheme('oasis')  -- Apply the theme
 ```
 
 </details>
 
 ## 🚀 Usage
 
-### ⭐ Recommended: Use `setup()` to launch nvim with your desired style
+### ⭐ Configuration and Application
+
+First, call `setup()` to configure Oasis, then apply the theme with `:colorscheme`:
 
 ```lua
--- Use default style (lagoon)
+-- Use default style
 require('oasis').setup()
+vim.cmd.colorscheme('oasis')
 
--- Or specify a style
+-- Or specify just one style
 require('oasis').setup({ style = "desert" })
+vim.cmd.colorscheme('oasis')
+
+-- Or choose dark / light styles (based on background)
+require('oasis').setup({ dark_style = "sol", light_style = "dawn" })
+vim.cmd.colorscheme('oasis')
 ```
 
-### Alternative: Use `colorscheme` command to swap on the fly
+### Switching Styles On The Fly
+
+After setup, use the `:colorscheme` command to swap between styles:
 
 ```lua
 vim.cmd.colorscheme("oasis")  -- default (lagoon)

lua/oasis/init.lua

@@ -13,7 +13,8 @@ function M.is_manual_bg_change(new_value)
 	return expected_background_value == new_value
 end
 
---- Setup Oasis with user configuration and apply the theme
+--- Setup Oasis with user configuration
+--- Note: This only configures Oasis. To apply the theme, use :colorscheme oasis
 --- Examples:
 ---   require('oasis').setup({
 ---     style = "lagoon",  -- Shorthand for "oasis_lagoon"
@@ -23,10 +24,10 @@ end
 ---     palette_overrides = { oasis_desert = { syntax = { comment = "#87CEEB" } } },
 ---     highlight_overrides = { Comment = { fg = "#AABBCC" } }
 ---   })
+---   vim.cmd.colorscheme('oasis')  -- Apply the theme
 ---@param user_config table|nil User configuration
 function M.setup(user_config)
 	config.setup(user_config)
-	M.apply()
 end
 
 --- Apply Oasis using a palette module name (no prefix).