fix(ssh): preserve path separators in scp:// URI construction

Problem: \`url_to_scp\` passes the file path through \`util.url_escape\`,
which encodes \`/\` as \`%2F\`. The resulting scp command uses a URI like
\`scp://host/%2Ftmp%2Ffile\` where percent-encoded slashes are not
treated as path separators, causing scp to fail with a connection
error.

Solution: unescape \`%2F\` back to \`/\` after encoding, so other special
characters (spaces, \`%\`, etc.) remain encoded but path separators are
preserved. The correct absolute-path URI form is \`scp://host//path\`.

lua/oil/adapters/ssh.lua

@@ -97,7 +97,7 @@ local function url_to_scp(url)
     table.insert(pieces, string.format(':%d', url.port))
   end
   table.insert(pieces, '/')
-  local escaped_path = util.url_escape(url.path)
+  local escaped_path = util.url_escape(url.path):gsub('%%2F', '/')
   table.insert(pieces, escaped_path)
   return table.concat(pieces, '')
 end