feat: add virtual text counter display

[subev]

Summary

• Add inline virtual text counter showing current reference position (e.g., [3/12])
• Counter displays at end of line where cursor jumps
• Automatically clears when highlights are cleared
• Configurable via new counter options

Changes

• New module: lua/refjump/counter.lua - handles virtual text display
• Modified: lua/refjump/jump.lua - calls counter instead of vim.notify
• Modified: lua/refjump/highlight.lua - clears counter with highlights
• Modified: lua/refjump/init.lua - adds counter configuration options

Configuration

require('refjump').setup({
  counter = {
    enable = true,        -- Enable/disable counter (default: true)
    hl_group = 'WarningMsg', -- Highlight group (default: bold orange)
  }
})

Demo

When jumping between references with ]r/[r, the counter appears at the end of the line:

• Shows [1/5], [2/5], etc.
• Bold orange text for high visibility
• Clears automatically when moving cursor or pressing escape

Replaces the previous vim.notify() notification with inline display inspired by nvim-hlslens.

[mawkler]

Thank you for your contribution!

I was also thinking that perhaps you should break out the logic for getting the current index and the total number of references to its own function. That way one could use it if they for example wanted to instead display that information in the statusline instead of using virtual text. That function would return the two values current_reference_index, total_reference_count (or with similar names). I notice however when looking through my code that we're passing around state a lot, including the references and current reference. So perhaps the best way would be to create a Lua "object" for storing that state. What do you think?

[mawkler]

I'd prefer if we always use the RefjumpCounter highlight group, and just link it to WarningMsg if it isn't set (that highlight group should always exist). You can thereby remove the counter.hl_group option.

[mawkler]

You should be able to refactor this to use vim.iter instead for a less imperative implementation, something like this (I haven't actually tried running it though):

local function find_reference_index(reference, references)
  local idx, _ = vim.iter(references):enumerate():find(function(i, ref)
    return ref.range.start.line == reference.range.start.line
       and ref.range.start.character == reference.range.start.character
  end)

  return idx
end

[mawkler]

I'd prefer if we did the check for counter.enable here before doing all this logic, instead of in require('refjump.counter').show(). And maybe break out this whole block to its own function, that you can wrap in if not require('refjump').get_options().counter.enable.

[subev]

Hey @mawkler, thanks for the feedback! I've addressed all your comments:
Changes made:

1. Removed counter.hl_group option - Now always using RefjumpCounter highlight group, linked to WarningMsg by default if not set by the user
2. Refactored find_reference_index() to use vim.iter - Cleaner functional style as you suggested
3. Moved counter.enable check to jump.lua - Created a show_counter() helper function that wraps the logic
4. Added state.lua module for statusline integration - As you suggested, I created a module to store per-buffer state and exposed get_reference_info() so users can display the counter in their statusline (e.g., lualine) instead of using virtual text
   Additional work:

• Added test infrastructure with plenary.nvim (12 tests for the state module)
• Updated CI workflow to run tests on push/PR
• Updated README with the new counter option, highlight groups documentation, and a lualine integration example