fix(ui): prevent style='minimal' from resetting window options on float update (#373)

Move `style = 'minimal'` from `base_config()` to `open_win()` so it
only applies during initial window creation via `nvim_open_win`.

Previously, `base_config()` included `style = 'minimal'` which was
shared by both `open_win()` and `update()`. Every time `update()` called
`nvim_win_set_config`, it re-applied `style = 'minimal'`, resetting
window-local options like `signcolumn` and `foldcolumn` back to their
minimal defaults. This caused the float window to lose its left gutter
(signcolumn + foldcolumn) after any resize or dimension update, unlike
the split layout which correctly retained these options.

Author: yct21

lua/opencode/ui/float_layout.lua

@@ -71,7 +71,6 @@ local function base_config(windows)
     height = height,
     row = resolve_position(float.row, vim.o.lines, height),
     col = resolve_position(float.col, vim.o.columns, width),
-    style = 'minimal',
     border = float.border,
   }
 end
@@ -114,6 +113,7 @@ end
 ---@param win_config vim.api.keyset.win_config
 ---@return integer
 function M.open_win(buf, enter, win_config)
+  win_config = vim.tbl_deep_extend('force', win_config, { style = 'minimal' })
   local win = vim.api.nvim_open_win(buf, enter, win_config)
   local float = config.ui.float or {}
   for opt, value in pairs(float.opts or {}) do