refactor(ui): simplify select rendering to avoid alignment issues

[epheien]

Summary

• Simplified the select rendering logic in lua/opencode/ui/select.lua
• Removed unnecessary indentation calculations that were causing alignment issues
• The change makes the code cleaner and more maintainable

Changes

• Removed the indent variable calculation based on item index
• Simplified group divider rendering to remove unnecessary spacing
• Simplified regular item formatting to remove the leading spacing

This refactoring improves the visual alignment of the select UI and reduces code complexity.

For example, when using dressing+telescope as the implementation of vim.ui.select, this situation occurs.

[NickvanDyke]

Ah, well this indentation is for the default vim.ui.select because it prepends the index number to each row. But I forgot about other vim.ui.select replacements. I wonder how we could only do this for the former case 🤔

[epheien]

Ah, well this indentation is for the default vim.ui.select because it prepends the index number to each row. But I forgot about other vim.ui.select replacements. I wonder how we could only do this for the former case 🤔

I know the purpose of doing it that way. What I mean is, if it's using the native vim.ui.select, then there's no need for padding, because it's hard to tell whether vim.ui.select is using the native one or another substitute.

[epheien]

I choose to modify the dressing code to solve this alignment issue.