refactor: rename oil to canola across entire codebase

Problem: the codebase still used the upstream \`oil\` naming everywhere —
URL schemes, the \`:Oil\` command, highlight groups, user events, module
paths, filetypes, buffer/window variables, LuaCATS type annotations,
vimdoc help tags, syntax groups, and internal identifiers.

Solution: mechanical rename of every reference. URL schemes now use
\`canola://\` (plus \`canola-ssh://\`, \`canola-s3://\`, \`canola-sss://\`,
\`canola-trash://\`, \`canola-test://\`). The \`:Canola\` command replaces
\`:Oil\`. All highlight groups, user events, augroups, namespaces,
filetypes, require paths, type annotations, help tags, and identifiers
follow suit. The \`upstream\` remote to \`stevearc/oil.nvim\` has been
removed and the \`vim.g.oil\` deprecation shim dropped.

lua/canola/adapters/trash/windows/powershell-trash.lua

@@ -0,0 +1,78 @@
+-- A wrapper around trash operations using windows powershell
+local Powershell = require('canola.adapters.trash.windows.powershell-connection')
+
+---@class canola.WindowsRawEntry
+---@field IsFolder boolean
+---@field DeletionDate integer
+---@field Name string
+---@field Path string
+---@field OriginalPath string
+
+local M = {}
+
+-- 0xa is the constant for Recycle Bin. See https://learn.microsoft.com/en-us/windows/win32/api/shldisp/ne-shldisp-shellspecialfolderconstants
+local list_entries_init = [[
+$shell = New-Object -ComObject 'Shell.Application'
+$folder = $shell.NameSpace(0xa)
+]]
+
+local list_entries_cmd = [[
+$data = @(foreach ($i in $folder.items())
+    {
+        @{
+            IsFolder=$i.IsFolder;
+            DeletionDate=([DateTimeOffset]$i.extendedproperty('datedeleted')).ToUnixTimeSeconds();
+            Name=$i.Name;
+            Path=$i.Path;
+            OriginalPath=-join($i.ExtendedProperty('DeletedFrom'), "\", $i.Name)
+        }
+    })
+ConvertTo-Json $data -Compress
+]]
+
+---@type nil|canola.PowershellConnection
+local list_entries_powershell
+
+---@param cb fun(err?: string, raw_entries?: canola.WindowsRawEntry[])
+M.list_raw_entries = function(cb)
+  if not list_entries_powershell then
+    list_entries_powershell = Powershell.new(list_entries_init)
+  end
+  list_entries_powershell:run(list_entries_cmd, function(err, string)
+    if err then
+      cb(err)
+      return
+    end
+
+    local ok, value = pcall(vim.json.decode, string)
+    if not ok then
+      cb(value)
+      return
+    end
+    cb(nil, value)
+  end)
+end
+
+-- 0 is the constant for Windows Desktop. See https://learn.microsoft.com/en-us/windows/win32/api/shldisp/ne-shldisp-shellspecialfolderconstants
+local delete_init = [[
+$shell = New-Object -ComObject 'Shell.Application'
+$folder = $shell.NameSpace(0)
+]]
+local delete_cmd = [[
+$path = Get-Item '%s'
+$folder.ParseName($path.FullName).InvokeVerb('delete')
+]]
+
+---@type nil|canola.PowershellConnection
+local delete_to_trash_powershell
+
+---@param path string
+---@param cb fun(err?: string)
+M.delete_to_trash = function(path, cb)
+  if not delete_to_trash_powershell then
+    delete_to_trash_powershell = Powershell.new(delete_init)
+  end
+  delete_to_trash_powershell:run((delete_cmd):format(path:gsub("'", "''")), cb)
+end
+
+return M