refactor: modularize nvim config into lua/config + lua/plugins

- Extract all options, keymaps, and autocommands into lua/config/
- Move every plugin spec into its own file under lua/plugins/
- Add custom inline orng colorscheme (dark + light) synced to macOS appearance
- Consolidate image.nvim into pdf-viewer.lua (fix duplicate spec)
- Fix image.nvim processor: magick -> magick_cli
- Remove conflicting nvim-autopairs (kept mini.pairs)
- Fix broken <C-f> keymap (was calling non-existent builtin cmd)
- Delete lua/kickstart/ and lua/custom/ folders
- Add colors/orng.vim + colors/orng-light.vim stubs for mid-session switching
- init.lua reduced from 1078 lines to 49 lines

lua/plugins/pdf-viewer.lua

@@ -0,0 +1,107 @@
+-- lua/plugins/pdf-viewer.lua
+-- PDF viewer using pdftoppm + image.nvim (kitty/magick backend)
+-- Requires: poppler (brew install poppler), kitty terminal
+
+return {
+  '3rd/image.nvim',
+  opts = {
+    backend = 'kitty',
+    processor = 'magick_cli',
+    integrations = {
+      markdown = { enabled = true },
+    },
+  },
+  config = function(_, opts)
+    local image = require 'image'
+    image.setup(opts)
+
+    local pdf_state = {}
+
+    -- Open PDF: convert all pages to PNG via pdftoppm, then display page 1
+    vim.api.nvim_create_autocmd('BufReadPost', {
+      pattern = '*.pdf',
+      callback = function()
+        local pdf_path = vim.fn.expand '%:p'
+        local temp_dir = vim.fn.tempname()
+        vim.fn.mkdir(temp_dir, 'p')
+        local bufnr = vim.api.nvim_get_current_buf()
+
+        vim.notify('Converting PDF…', vim.log.levels.INFO)
+
+        vim.fn.jobstart({ 'pdftoppm', '-png', pdf_path, temp_dir .. '/page' }, {
+          on_exit = function(_, code)
+            vim.schedule(function()
+              if code ~= 0 then
+                vim.notify('Failed to convert PDF', vim.log.levels.ERROR)
+                return
+              end
+
+              -- Count pages
+              local handle = vim.loop.fs_scandir(temp_dir)
+              local page_count = 0
+              if handle then
+                while true do
+                  local name = vim.loop.fs_scandir_next(handle)
+                  if not name then break end
+                  if name:match '^page%-%d+%.png$' then page_count = page_count + 1 end
+                end
+              end
+
+              pdf_state[bufnr] = { temp_dir = temp_dir, current_page = 1, total_pages = page_count }
+
+              local function show_page(page_num)
+                local state = pdf_state[bufnr]
+                if not state then return end
+                image.clear()
+                vim.bo[bufnr].modifiable = true
+                vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, { '' })
+                vim.bo[bufnr].modifiable = false
+                local page_file = string.format('%s/page-%02d.png', state.temp_dir, page_num)
+                local img = image.from_file(page_file, { buffer = bufnr })
+                if img then
+                  img:render()
+                  vim.notify(string.format('Page %d / %d', page_num, state.total_pages), vim.log.levels.INFO)
+                else
+                  vim.notify('Failed to load page ' .. page_num, vim.log.levels.ERROR)
+                end
+              end
+
+              local function change_page(delta)
+                local state = pdf_state[bufnr]
+                if not state then return end
+                local new_page = state.current_page + delta
+                if new_page < 1 or new_page > state.total_pages then return end
+                state.current_page = new_page
+                show_page(new_page)
+              end
+
+              -- Buffer-local navigation keys
+              local map = function(lhs, fn, desc)
+                vim.keymap.set('n', lhs, fn, { buffer = bufnr, desc = desc })
+              end
+              map('j',       function() change_page(1) end,  'PDF: next page')
+              map('k',       function() change_page(-1) end, 'PDF: previous page')
+              map('<Right>', function() change_page(1) end,  'PDF: next page')
+              map('<Left>',  function() change_page(-1) end, 'PDF: previous page')
+              map('q', '<cmd>bd!<cr>', 'PDF: close')
+
+              show_page(1)
+            end)
+          end,
+        })
+      end,
+    })
+
+    -- Cleanup temp files on buffer close
+    vim.api.nvim_create_autocmd('BufDelete', {
+      pattern = '*.pdf',
+      callback = function(args)
+        if pdf_state[args.buf] then
+          image.clear()
+          vim.fn.delete(pdf_state[args.buf].temp_dir, 'rf')
+          pdf_state[args.buf] = nil
+        end
+      end,
+    })
+  end,
+}