Implement custom tabline with configurable path shortening

Add a custom tabline function to enhance path display in Neovim.
Users can configure the number of full parent directories and the
length of shortened directory names for better context and
manageability.

lua/settings.lua

@@ -16,6 +16,26 @@ vim.opt.autochdir = false -- Keep working directory at project root
 vim.opt.exrc = true -- Load .nvim.lua from project root
 vim.opt.secure = true -- Prompt before loading untrusted files
 
+-- Custom tabline configuration
+-- Load utils module for custom tabline function
+local utils = require('utils')
+
+-- Configure number of parent directories to show in full (default: 1)
+-- Examples:
+--   1: /path/to/my/project/src/file.txt → pat/to/my/project/src/file.txt
+--   2: /path/to/my/project/src/file.txt → pat/to/my/project/src/file.txt
+utils.tabline_full_parents = 1
+
+-- Configure number of characters to show for shortened directories (default: 3)
+-- Examples:
+--   3: /path/to/my → pat/to/my
+--   1: /path/to/my → p/t/m
+utils.tabline_shorten_length = 4
+
+-- Use custom tabline function
+vim.opt.tabline = '%!v:lua.require("utils").custom_tabline()'
+vim.opt.showtabline = 1 -- Show tabline only when there are 2+ tabs
+
 -- Phase 3.2: non-plugin settings (legacy values where specified)
 -- Completion UI for nvim-cmp
 vim.opt.completeopt = { "menu", "menuone", "noselect" }