ArWen 1.3.1

Four commands take a fresh machine to a rendered forecast: pip install gpuwm[gpu,render], gpuwm setup, gpuwm domain, gpuwm go.
Physics combination admission follows WRF v4.6.1's own compatibility
verdicts, the run-time parameter ledger is closed out with every
unimplemented parameter refusing by name, polar stereographic and
Mercator projections run end to end, and mixed microphysics across a
nest edge runs under a named transition policy.

The four-command chain

• Both forecast runners live in the installed package. python -m gpuwm.prepared_single_domain_forecast and python -m gpuwm.prepared_domain_tree_forecast work from any directory, with
  console scripts gpuwm-prepared-forecast and
  gpuwm-prepared-tree-forecast; the tools/ scripts a checkout
  carries delegate to the same module objects, so no second copy
  exists to drift. Every command the CLI prints is one a pip install
  can execute. In 1.3.0 the chain's last two stages were spelled as
  relative script paths only a git checkout has.
• gpuwm go <config> runs the whole single-domain GFS chain as six
  stages in one invocation -- authority, fetch, manifest, prepare,
  forecast, render -- and prints a heartbeat every 20 seconds with
  the stage's elapsed time and, where the stage publishes one, its
  model seconds. Rendering is the sixth stage rather than a command
  to paste; a missing render extra is named instead of skipped.
• A refused stage speaks in sentences. A reused output directory is
  refused up front with the directory named, why it is create-only,
  and both ways out; in 1.3.0 this surfaced as a raw
  FileExistsError traceback from a flag the caller never typed.
• gpuwm go drives one domain from GFS. A multi-domain tree is
  refused up front and the refusal names
  python -m gpuwm.prepared_domain_tree_forecast.

The wizard composes with go

• gpuwm domain at a bare prompt asks its questions and emits a
  config gpuwm go accepts: one 12 km domain on the model-validated
  morrison-mp10-ysu-mm5-noah-kf-rte-rrtmgp-v1 profile, with both
  supplied defaults stated in the session. This changes the
  bare-session emission -- in 1.3.0 it was a four-domain ladder on
  the product default suite, a shape the single-domain chain refuses
  twice over. Pass --ladder for nests and --physics-profile for
  another suite; a session with any explicit flag keeps the flag
  path's own defaults.
• The closing next-steps block branches on source: a GFS emission
  ends at gpuwm go, an ERA5 emission keeps gpuwm run, and HRRR
  and multi-domain trees get their route named. In 1.3.0 the block
  ended at gpuwm run for every source, and gpuwm run refuses GFS
  configs by design.
• A domain sized to fill the card prints an advisory when its fetch
  box exceeds 90 degrees of longitude, naming --vram-gib for a
  smaller first run. Sizing itself is unchanged, and continental
  domains under the threshold pass without comment.

WRF v4.6.1 combination admission

The combination authority is a 2,400-cell transcription of WRF
v4.6.1's own PBL, surface-layer, and land-surface admission: 1,080
cells legal, 360 legal with WRF's silent reconfiguration named, 600
fatal, 360 not expressible in WRF. Three pairings 1.3.0 refused are
admitted because WRF admits them -- PBL off with the MYNN surface
layer, and MYNN PBL with either MM5 surface layer, each across the
four routed land models -- and refusals cite the matrix cell that
produced them. An edge policy is not a loophole: a PBL/surface-layer
pairing the matrix calls fatal refuses whatever the nest declares.

Run-time parameters

The declared WRF namelist parameter set stands at 158: 104
implemented, and each of the 54 others refuses by name with the
blocking dependency cited. Five parameters whose runtime branches
already existed are wired end to end: isfflx, o3input,
use_mp_re, seaice_albedo_default (replacing a live-path
literal), and rdmaxalb.

Projections

Polar stereographic and Mercator domains run end to end -- wizard
emission, WPS namelist, static-field preparation, map factors, and
earth-relative wind rotation -- verified against WPS geogrid
references for both families. A bare interactive session at high
latitude emits map_proj = "polar" with a matching namelist.

Nest edges

All 20 ordered pairs of ported microphysics schemes run across a
parent-child edge under an explicit nest_microphysics_transition
policy, and a mixed edge without one refuses naming the setting.
Each policy's mass and number handling is a registry row with its
WRF citation, not a code path a config reaches silently.

Byte-stable checkouts

.gitattributes declares * -text: a clone materializes the
committed bytes on every platform. That immediately exposed one
shipped defect, fixed here -- the packaged GFS Vtable's hash
contract named the file's CRLF form, which only a Windows checkout
produced. The contract names the committed bytes, and
tests/test_line_ending_stability.py holds every hashed-contract
file to its blob.

Fixed

• gpuwm go's render stage handed the render CLI the wrfout
  directory rather than its frames, failing after a successful
  forecast. Found driving this release's own acceptance chain; the
  frames are enumerated, and --dry-run still prints the glob.
• --materialize-authorities refused a reused output directory with
  a raw traceback; a missing base input did the same. Both are
  sentences.
• The packaged GFS Vtable hash pin, above.

The four certified profiles are byte-identical to 1.3.0: their
pinned two-step trajectory hashes did not move, and the registry
regenerates to the tracked bytes.