XDVD media profile write_media_state
====================================

This source update extends the option-1 media profile writer.  The dumper still
emits the existing files:

  <title>[media].iso
  <title>[media].xdvd.json
  <title>[media].media.json
  <title>[media].ad_c0.bin
  <title>[media].pfi.bin
  <title>[media].dmi.bin

The .media.json file now includes a top-level write_media_state block for the
inserted media.  For dumped Xbox retail media this block is intentionally
read-only:

  media_class: pressed_dvd_rom
  writable: false
  erasable: false
  finalized: true
  backing_image.growth_policy: fixed_read_only

This keeps the same schema shape as writable/erasable media profiles used by
the emulator, while accurately describing a pressed Xbox DVD-ROM image.  Blank
or appendable media images should use the same write_media_state schema but set
media_class/writable/erasable/finalized/sessions/tracks according to the target
virtual medium.
