refactor: revert canola namespace to oil and remove vim.g config (#120)

* refactor: revert module namespace from canola back to oil

Problem: the canola rename creates unnecessary friction for users
migrating from stevearc/oil.nvim — every `require('oil')` call and
config reference must change.

Solution: revert all module paths, URL schemes, autocmd groups,
highlight groups, and filetype names back to `oil`. The repo stays
`canola.nvim` for identity; the code is a drop-in replacement.

* refactor: remove `vim.g.oil` declarative config

Problem: the `vim.g.oil` configuration path was added prematurely.
It adds a second config entrypoint before the plugin has stabilized
enough to justify it.

Solution: remove `vim.g.oil` support from `plugin/oil.lua`,
`config.setup()`, docs, and tests. Users configure via
`require("oil").setup({})`.

lua/oil/mutator/progress.lua

@@ -0,0 +1,223 @@
+local columns = require('oil.columns')
+local config = require('oil.config')
+local layout = require('oil.layout')
+local loading = require('oil.loading')
+local util = require('oil.util')
+local Progress = {}
+
+local FPS = 20
+
+function Progress.new()
+  return setmetatable({
+    lines = { '', '' },
+    count = '',
+    spinner = '',
+    bufnr = nil,
+    winid = nil,
+    min_bufnr = nil,
+    min_winid = nil,
+    autocmds = {},
+    closing = false,
+  }, {
+    __index = Progress,
+  })
+end
+
+---@private
+---@return boolean
+function Progress:is_minimized()
+  return not self.closing
+    and not self.bufnr
+    and self.min_bufnr
+    and vim.api.nvim_buf_is_valid(self.min_bufnr)
+end
+
+---@param opts nil|table
+---    cancel fun()
+function Progress:show(opts)
+  opts = opts or {}
+  if self.winid and vim.api.nvim_win_is_valid(self.winid) then
+    return
+  end
+  local bufnr = vim.api.nvim_create_buf(false, true)
+  vim.bo[bufnr].bufhidden = 'wipe'
+  self.bufnr = bufnr
+  self.cancel = opts.cancel or self.cancel
+  local loading_iter = loading.get_bar_iter()
+  local spinner = loading.get_iter('dots')
+  if not self.timer then
+    self.timer = vim.loop.new_timer()
+    self.timer:start(
+      0,
+      math.floor(1000 / FPS),
+      vim.schedule_wrap(function()
+        self.lines[2] = string.format('%s %s', self.count, loading_iter())
+        self.spinner = spinner()
+        self:_render()
+      end)
+    )
+  end
+  local width, height = layout.calculate_dims(120, 10, config.progress)
+  self.winid = vim.api.nvim_open_win(self.bufnr, true, {
+    relative = 'editor',
+    width = width,
+    height = height,
+    row = math.floor((layout.get_editor_height() - height) / 2),
+    col = math.floor((layout.get_editor_width() - width) / 2),
+    zindex = 152, -- render on top of the floating window title
+    style = 'minimal',
+    border = config.progress.border,
+  })
+  vim.bo[self.bufnr].filetype = 'oil_progress'
+  for k, v in pairs(config.progress.win_options) do
+    vim.api.nvim_set_option_value(k, v, { scope = 'local', win = self.winid })
+  end
+  table.insert(
+    self.autocmds,
+    vim.api.nvim_create_autocmd('VimResized', {
+      callback = function()
+        self:_reposition()
+      end,
+    })
+  )
+  table.insert(
+    self.autocmds,
+    vim.api.nvim_create_autocmd('WinLeave', {
+      callback = function()
+        self:minimize()
+      end,
+    })
+  )
+  local cancel = self.cancel or function() end
+  local minimize = function()
+    if self.winid and vim.api.nvim_win_is_valid(self.winid) then
+      vim.api.nvim_win_close(self.winid, true)
+    end
+  end
+  vim.keymap.set('n', 'c', cancel, { buffer = self.bufnr, nowait = true })
+  vim.keymap.set('n', 'C', cancel, { buffer = self.bufnr, nowait = true })
+  vim.keymap.set('n', 'm', minimize, { buffer = self.bufnr, nowait = true })
+  vim.keymap.set('n', 'M', minimize, { buffer = self.bufnr, nowait = true })
+end
+
+function Progress:restore()
+  if self.closing then
+    return
+  elseif not self:is_minimized() then
+    error('Cannot restore progress window: not minimized')
+  end
+  self:_cleanup_minimized_win()
+  self:show()
+end
+
+function Progress:_render()
+  if self.bufnr and vim.api.nvim_buf_is_valid(self.bufnr) then
+    util.render_text(
+      self.bufnr,
+      self.lines,
+      { winid = self.winid, actions = { '[M]inimize', '[C]ancel' } }
+    )
+  end
+  if self.min_bufnr and vim.api.nvim_buf_is_valid(self.min_bufnr) then
+    util.render_text(
+      self.min_bufnr,
+      { string.format('%sOil: %s', self.spinner, self.count) },
+      { winid = self.min_winid, h_align = 'left' }
+    )
+  end
+end
+
+function Progress:_reposition()
+  if self.winid and vim.api.nvim_win_is_valid(self.winid) then
+    local min_width = 120
+    local line_width = vim.api.nvim_strwidth(self.lines[1])
+    if line_width > min_width then
+      min_width = line_width
+    end
+    local width, height = layout.calculate_dims(min_width, 10, config.progress)
+    vim.api.nvim_win_set_config(self.winid, {
+      relative = 'editor',
+      width = width,
+      height = height,
+      row = math.floor((layout.get_editor_height() - height) / 2),
+      col = math.floor((layout.get_editor_width() - width) / 2),
+      zindex = 152, -- render on top of the floating window title
+    })
+  end
+end
+
+function Progress:_cleanup_main_win()
+  if self.winid then
+    if vim.api.nvim_win_is_valid(self.winid) then
+      vim.api.nvim_win_close(self.winid, true)
+    end
+    self.winid = nil
+  end
+  for _, id in ipairs(self.autocmds) do
+    vim.api.nvim_del_autocmd(id)
+  end
+  self.autocmds = {}
+  self.bufnr = nil
+end
+
+function Progress:_cleanup_minimized_win()
+  if self.min_winid and vim.api.nvim_win_is_valid(self.min_winid) then
+    vim.api.nvim_win_close(self.min_winid, true)
+  end
+  self.min_winid = nil
+  self.min_bufnr = nil
+end
+
+function Progress:minimize()
+  if self.closing then
+    return
+  end
+  self:_cleanup_main_win()
+  local bufnr = vim.api.nvim_create_buf(false, true)
+  vim.bo[bufnr].bufhidden = 'wipe'
+  local winid = vim.api.nvim_open_win(bufnr, false, {
+    relative = 'editor',
+    width = 16,
+    height = 1,
+    anchor = 'SE',
+    row = layout.get_editor_height(),
+    col = layout.get_editor_width(),
+    zindex = 152, -- render on top of the floating window title
+    style = 'minimal',
+    border = config.progress.minimized_border,
+  })
+  self.min_bufnr = bufnr
+  self.min_winid = winid
+  self:_render()
+  vim.notify_once('Restore progress window with :Oil --progress')
+end
+
+---@param action oil.Action
+---@param idx integer
+---@param total integer
+function Progress:set_action(action, idx, total)
+  local adapter = util.get_adapter_for_action(action)
+  local change_line
+  if action.type == 'change' then
+    ---@cast action oil.ChangeAction
+    change_line = columns.render_change_action(adapter, action)
+  else
+    change_line = adapter.render_action(action)
+  end
+  self.lines[1] = change_line
+  self.count = string.format('%d/%d', idx, total)
+  self:_reposition()
+  self:_render()
+end
+
+function Progress:close()
+  self.closing = true
+  if self.timer then
+    self.timer:close()
+    self.timer = nil
+  end
+  self:_cleanup_main_win()
+  self:_cleanup_minimized_win()
+end
+
+return Progress