feat(nvim): add copy_ref plugin for AI chat references

Adds a scratch buffer-based utility to copy file paths and line
ranges for pasting into AI chat conversations. Supports normal mode
(copy path), visual mode (copy path:start:end), and a scratch buffer
for collecting multiple references.

config/nvim/after/plugin/keymaps.lua

@@ -42,7 +42,6 @@ vim.keymap.set("n", "<leader>bn", "<cmd>enew<cr>", { desc = "New File" })
 -- vim.keymap.set("n", "<leader>bd", "<cmd>bdelete<cr>", { desc = "Unload Buffer" })
 
 vim.keymap.set("n", "<leader>`", "<cmd>e #<cr>", { desc = "Switch to Other Buffer" })
-vim.keymap.set("n", "<leader>bc", "<cmd>tabclose<cr>", { desc = "Close Tab" })
 
 -- Clear search with <esc>
 vim.keymap.set('n', '<Esc>', '<cmd>nohlsearch<cr>', { desc = "clear hlsearch" })