Add fzf-lua for project navigation

Wraps the fzf binary already installed via brew, alongside rg and fd,
so it needs no plugin dependencies - unlike telescope, which would
also pull in plenary. Picks up nvim-web-devicons for file icons, which
is the first thing actually using that plugin.

Maps live under <leader>f: files, live grep, buffers, grep the word
under the cursor, and help tags. The intent is to stop treating netrw
as the way into a project and switch to jumping by name, leaving
buffers open and bouncing between them, rather than quitting out of
nvim to change file.

Netrw is untouched and still on :Ex for browsing an unfamiliar tree.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

neovim/config/plugins/fzf-lua.lua

@@ -0,0 +1,15 @@
+vim.pack.add({ 'https://github.com/ibhagwan/fzf-lua' })
+
+local fzf = require('fzf-lua')
+
+fzf.setup()
+
+local function map(lhs, rhs, desc)
+  vim.keymap.set('n', lhs, rhs, { desc = desc })
+end
+
+map('<leader>ff', fzf.files, 'Find files')
+map('<leader>fg', fzf.live_grep, 'Grep project')
+map('<leader>fb', fzf.buffers, 'Switch buffer')
+map('<leader>fw', fzf.grep_cword, 'Grep word under cursor')
+map('<leader>fh', fzf.helptags, 'Search help')