WIP .dcf handling

[cursork]

Building on top of previous work to support 220⌶, this handles basic .dcf file reading/writing, without calling out to APL. It is currently known to be buggy and extremely incomplete, however, some simple files generated from v20 can have their data inspected in the data browser.

dcf.mp4

A new binary exists: apldcf. Same simple data only component file as before:

file:      ../../dcf/testdata/three_components.dcf
version:   0x14
ptr_size:  8
created:   2026-05-18 22:34:24 UTC
components: 3 (numbers 1..3)

  #   ⎕DR  rank  shape
  1    80   1     [5]
  2    83   1     [10]
  3    83   2     [2 3]