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/lsp/helpers.lua

@@ -0,0 +1,121 @@
+local config = require('oil.config')
+local fs = require('oil.fs')
+local util = require('oil.util')
+local workspace = require('oil.lsp.workspace')
+
+local M = {}
+
+---@param actions oil.Action[]
+---@return fun() did_perform Call this function when the file operations have been completed
+M.will_perform_file_operations = function(actions)
+  local moves = {}
+  local creates = {}
+  local deletes = {}
+  for _, action in ipairs(actions) do
+    if action.type == 'move' then
+      local src_scheme, src_path = util.parse_url(action.src_url)
+      assert(src_path)
+      local src_adapter = assert(config.get_adapter_by_scheme(src_scheme))
+      local dest_scheme, dest_path = util.parse_url(action.dest_url)
+      local dest_adapter = assert(config.get_adapter_by_scheme(dest_scheme))
+      src_path = fs.posix_to_os_path(src_path)
+      dest_path = fs.posix_to_os_path(assert(dest_path))
+      if src_adapter.name == 'files' and dest_adapter.name == 'files' then
+        moves[src_path] = dest_path
+      elseif src_adapter.name == 'files' then
+        table.insert(deletes, src_path)
+      elseif dest_adapter.name == 'files' then
+        table.insert(creates, src_path)
+      end
+    elseif action.type == 'create' then
+      local scheme, path = util.parse_url(action.url)
+      path = fs.posix_to_os_path(assert(path))
+      local adapter = assert(config.get_adapter_by_scheme(scheme))
+      if adapter.name == 'files' then
+        table.insert(creates, path)
+      end
+    elseif action.type == 'delete' then
+      local scheme, path = util.parse_url(action.url)
+      path = fs.posix_to_os_path(assert(path))
+      local adapter = assert(config.get_adapter_by_scheme(scheme))
+      if adapter.name == 'files' then
+        table.insert(deletes, path)
+      end
+    elseif action.type == 'copy' then
+      local scheme, path = util.parse_url(action.dest_url)
+      path = fs.posix_to_os_path(assert(path))
+      local adapter = assert(config.get_adapter_by_scheme(scheme))
+      if adapter.name == 'files' then
+        table.insert(creates, path)
+      end
+    end
+  end
+
+  local buf_was_modified = {}
+  for _, bufnr in ipairs(vim.api.nvim_list_bufs()) do
+    buf_was_modified[bufnr] = vim.bo[bufnr].modified
+  end
+
+  local edited_uris = {}
+  local final_err = nil
+  ---@param edits nil|{edit: lsp.WorkspaceEdit, client_offset: string}[]
+  local function accum(edits, err)
+    final_err = final_err or err
+    if edits then
+      for _, edit in ipairs(edits) do
+        if edit.edit.changes then
+          for uri in pairs(edit.edit.changes) do
+            edited_uris[uri] = true
+          end
+        end
+        if edit.edit.documentChanges then
+          for _, change in ipairs(edit.edit.documentChanges) do
+            if change.textDocument then
+              edited_uris[change.textDocument.uri] = true
+            end
+          end
+        end
+      end
+    end
+  end
+  local timeout_ms = config.lsp_file_methods.timeout_ms
+  accum(workspace.will_create_files(creates, { timeout_ms = timeout_ms }))
+  accum(workspace.will_delete_files(deletes, { timeout_ms = timeout_ms }))
+  accum(workspace.will_rename_files(moves, { timeout_ms = timeout_ms }))
+  if final_err then
+    vim.notify(
+      string.format('[lsp] file operation error: %s', vim.inspect(final_err)),
+      vim.log.levels.WARN
+    )
+  end
+
+  return function()
+    workspace.did_create_files(creates)
+    workspace.did_delete_files(deletes)
+    workspace.did_rename_files(moves)
+
+    local autosave = config.lsp_file_methods.autosave_changes
+    if autosave == false then
+      return
+    end
+    for uri, _ in pairs(edited_uris) do
+      local bufnr = vim.uri_to_bufnr(uri)
+      local was_open = buf_was_modified[bufnr] ~= nil
+      local was_modified = buf_was_modified[bufnr]
+      local should_save = autosave == true or (autosave == 'unmodified' and not was_modified)
+      -- Autosave changed buffers if they were not modified before
+      if should_save then
+        vim.api.nvim_buf_call(bufnr, function()
+          vim.cmd.update({ mods = { emsg_silent = true, noautocmd = true } })
+        end)
+
+        -- Delete buffers that weren't open before
+        if not was_open then
+          vim.api.nvim_buf_delete(bufnr, { force = true })
+        end
+      end
+    end
+  end
+end
+
+return M