pass 1: get rid of obsolete modules

lua/u/codewriter.lua

@@ -1,5 +1,3 @@
-local Buffer = require 'u.buffer'
-
 --- @class u.CodeWriter
 --- @field lines string[]
 --- @field indent_level number
@@ -25,7 +23,8 @@ end
 
 --- @param p u.Pos
 function CodeWriter.from_pos(p)
-  local line = Buffer.from_nr(p.bufnr):line(p.lnum):text()
+  local Range = require 'u.range'
+  local line = Range.from_line(p.bufnr, p.lnum):text()
   return CodeWriter.from_line(line, p.bufnr)
 end