refinement_stepper: compatibility views are kept on purpose (comment only)

The views and the PeriodicPatchStepper alias stay for the existing tests
and docs (about 130 references); the comment no longer says REMOVE AFTER.
No code change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/supported_settings.md

@@ -1,6 +1,7 @@
-# Supported settings: 2D Jet + fixed multilevel refinement (candidate c95a7ba)
+# Supported settings: 2D Jet + fixed multilevel refinement (candidate 888c8038)
 
-Every entry names the guard that enforces it (file:line at c95a7ba) and, where one
+Every entry names the guard that enforces it (file and function or kernel guard,
+at source revision 888c80381c006e976be2af8a452288729fc17c1b) and, where one
 exists, an existing test that exercises it. A setting not listed here is not
 claimed. Observations at the end are tied to the exact case in which they were
 measured; they are not general bounds.
@@ -9,12 +10,12 @@ measured; they are not general bounds.
 
 | Setting | Supported | Guard |
 |---|---|---|
-| Dimension / lattice | 2D D2Q9 only (3D refinement is future work) | `lbm/refinement.py:65`, `lbm/kernels/blocks.cu:25`, `lbm/kernels/refinement.cu:26` |
+| Dimension / lattice | 2D D2Q9 only (3D refinement is future work) | `lbm/refinement.py` `FixedPatch2D.from_config`; `#error` guards in `lbm/kernels/blocks.cu` and `lbm/kernels/refinement.cu` |
 | Precision / streaming | FP32 storage, double buffer | same guards |
-| Collision on refinement levels | SRT or MRT; TRT and LES rejected | `lbm/refinement.py:65` (re-checked for fine boundaries at `lbm/refinement.py:457`) |
-| Shifted (ddf_shifting) storage | only when every level is blocked; dense or mixed rejected | `lbm/refinement_stepper.py:198`, `:469`; `lbm/kernels/refinement.cu:26` (dense patch kernel unshifted only) |
-| Fine relaxation | 1/tau_fine must lie inside the configured omega guards | `lbm/refinement.py:80` |
-| Uniform blocked backend `PeriodicBlockStepper` | doubly periodic, SRT only, stationary passive circles | `lbm/block_stepper.py:84`, `:91`, `:45`-`:67` |
+| Collision on refinement levels | SRT or MRT; TRT and LES rejected | `lbm/refinement.py` `FixedPatch2D.from_config` (re-checked for fine boundaries in `prepare_fine_boundary`) |
+| Shifted (ddf_shifting) storage | only when every level is blocked; dense or mixed rejected | `lbm/refinement_stepper.py` `FixedPatchStepper.__init__`, `FixedPatchStepper._check_storage`; `#error` guard in `lbm/kernels/refinement.cu` (dense patch kernel unshifted only) |
+| Fine relaxation | 1/tau_fine must lie inside the configured omega guards | `lbm/refinement.py` `FixedPatch2D.from_config` |
+| Uniform blocked backend `PeriodicBlockStepper` | doubly periodic, SRT only, stationary passive circles | `lbm/block_stepper.py` `PeriodicBlockStepper.__init__`, `_static_circles` |
 
 Tests: `tests/unit/test_refinement_mrt.py`, `tests/validation/multigrid/test_refinement_mrt_gpu.py`,
 `tests/unit/test_shifted_storage.py`, `tests/unit/test_shifted_block_operators.py`.
@@ -23,17 +24,17 @@ Tests: `tests/unit/test_refinement_mrt.py`, `tests/validation/multigrid/test_ref
 
 | Setting | Supported | Guard |
 |---|---|---|
-| Depth | at least one refinement level; one entry per level in `level_blocks`/`level_objects`/`level_jets` | `lbm/refinement_stepper.py:72`, `:75` |
-| Single L1 rectangle | two-coarse-cell margin to the domain edge | `lbm/refinement.py:73` |
-| Several L1 rectangles (union) | require `level_blocks[0]` and `level_blocks[1]`; transfers must close (dependency checks, no fixed gap rule) | `lbm/refinement_stepper.py:84`; `lbm/refinement.py:283`-`:295` |
-| Nested levels | depth >= 3 must be all blocked; a blocked level requires blocked levels below; a scalar child needs a scalar parent | `lbm/refinement_stepper.py:82`, `:87`; `lbm/hierarchy.py:54` |
-| Nested transfer support | child only over inherited ACTIVE cells, donors/receivers uncovered ACTIVE, no child over the parent restriction footprint | `lbm/refinement.py:391`-`:407` |
-| Tile shape | positive `(by, bx)`; the level allocation must be divisible by the tile (no partial tiles yet) | `lbm/refinement_stepper.py:78`, `lbm/refinement.py:246` (shape); `lbm/blocks.py:134` (divisibility) |
-| Coarse boundary | `periodic`, `slot_reservoir` or `channel` | `lbm/refinement_stepper.py:177` |
-| `slot_reservoir` | on-site velocity bottom slot, reservoir top, velocity 0, 2 <= slot width < nx, patch rows 4..ny-4 | `lbm/refinement_stepper.py:205`, `:212`; `lbm/refinement.py:546` |
-| `channel` | all levels blocked; Zou-He inlet, pressure-NEQ outlet, stationary bounce-back walls; transfers away from the closure | `lbm/channel.py:22`, `:26`, `:43`, `:54` |
-| Explosion | `constant` (default); `projected_linear` only periodic, all-blocked SRT, no bodies/Jets, no LES (experimental) | `lbm/refinement_stepper.py:188`, `:193` |
-| L2 runtime remap (`remap_child`) | periodic three-level L2 sets only, no L0/L1 bodies, identical pinned boundary | `lbm/refinement_stepper.py:557`, `:567`-`:581` |
+| Depth | at least one refinement level; one entry per level in `level_blocks`/`level_objects`/`level_jets` | `lbm/refinement_stepper.py` `_check_levels` |
+| Single L1 rectangle | two-coarse-cell margin to the domain edge | `lbm/refinement.py` `FixedPatch2D.from_config` |
+| Several L1 rectangles (union) | require `level_blocks[0]` and `level_blocks[1]`; transfers must close (dependency checks, no fixed gap rule) | `lbm/refinement_stepper.py` `_check_levels`; `lbm/refinement.py` `_check_parent_pull_closure` |
+| Nested levels | depth >= 3 must be all blocked; a blocked level requires blocked levels below; a scalar child needs a scalar parent | `lbm/refinement_stepper.py` `_check_levels`; `lbm/hierarchy.py` `build_hierarchy` |
+| Nested transfer support | child only over inherited ACTIVE cells, donors/receivers uncovered ACTIVE, no child over the parent restriction footprint | `lbm/refinement.py` `_nested_kind` |
+| Tile shape | positive `(by, bx)`; the level allocation must be divisible by the tile (no partial tiles yet) | `lbm/refinement_stepper.py` `_check_levels`, `lbm/refinement.py` `FixedPatchSet2D.fine_layout` (shape); `lbm/blocks.py` `BlockLayout2D.build` (divisibility) |
+| Coarse boundary | `periodic`, `slot_reservoir` or `channel` | `lbm/refinement_stepper.py` `FixedPatchStepper.__init__` |
+| `slot_reservoir` | on-site velocity bottom slot, reservoir top, velocity 0, 2 <= slot width < nx, patch rows 4..ny-4 | `lbm/refinement_stepper.py` `FixedPatchStepper.__init__`; `lbm/refinement.py` `prepare_fine_boundary` |
+| `channel` | all levels blocked; Zou-He inlet, pressure-NEQ outlet, stationary bounce-back walls; transfers away from the closure | `lbm/channel.py` `validate_channel_config`, `validate_channel_transfers` |
+| Explosion | `constant` (default); `projected_linear` only periodic, all-blocked SRT, no bodies/Jets, no LES (experimental) | `lbm/refinement_stepper.py` `FixedPatchStepper.__init__` |
+| L2 runtime remap (`remap_child`) | periodic three-level L2 sets only, no L0/L1 bodies, identical pinned boundary | `lbm/refinement_stepper.py` `FixedPatchStepper.remap_child` |
 
 Tests: `tests/unit/test_refinement_three_level_multipatch.py`, `tests/validation/multigrid/test_refinement_multipatch.py`,
 `test_refinement_three_level.py`, `test_refinement_three_level_multipatch_gpu.py`, `test_refinement_blocked_base.py`,
@@ -44,14 +45,14 @@ Tests: `tests/unit/test_refinement_three_level_multipatch.py`, `tests/validation
 
 | Setting | Supported | Guard |
 |---|---|---|
-| Bodies | stationary circles without sensor/force-region roles, entirely inside the patch union, fully resolved, disjoint, stencil away from the two-hop transfer footprint | `lbm/refinement.py:474`-`:542` |
-| Level | not on L0; only on the finest level of a nested hierarchy | `lbm/refinement_stepper.py:80`, `:89` |
-| Jet condition | velocity only; `pressure` is reserved and raises NotImplementedError | `body/jets.py:148`, `:150` |
-| Jet geometry | each Jet selects resolved links of exactly one stationary body; no Jet/Jet or Jet/SurfaceActuation overlap; abs(amplitude) < 1 lattice | `body/jets.py:155`, `:175`, `:177`, `:255`, `:261`, `:263` |
-| Jets with shifted storage | only in the all-blocked stepper with SRT and no LES | `body/jets.py:249` |
-| SurfaceActuation | unshifted storage only | `body/objects.py:155` |
-| Raw boundary exchange (force) | blocked body levels only; the window ledger requires `observe_raw_exchange` | `lbm/refinement_stepper.py:264`, `:269` |
-| Checkpoint with Jets | refused | `simulation.py:687` |
+| Bodies | stationary circles without sensor/force-region roles, entirely inside the patch union, fully resolved, disjoint, stencil away from the two-hop transfer footprint | `lbm/refinement.py` `prepare_fine_boundary` |
+| Level | not on L0; only on the finest level of a nested hierarchy | `lbm/refinement_stepper.py` `_check_levels` |
+| Jet condition | velocity only; `pressure` is reserved and raises NotImplementedError | `body/jets.py` `Jet.__post_init__` |
+| Jet geometry | each Jet selects resolved links of exactly one stationary body; no Jet/Jet or Jet/SurfaceActuation overlap; abs(amplitude) < 1 lattice | `body/jets.py` `Jet.__post_init__`, `jet_link_shapes`, `_surface_links` |
+| Jets with shifted storage | only in the all-blocked stepper with SRT and no LES | `body/jets.py` `_surface_links` |
+| SurfaceActuation | unshifted storage only | `body/objects.py` `SimObject.validate_surface_actuation` |
+| Raw boundary exchange (force) | blocked body levels only; the window ledger requires `observe_raw_exchange` | `lbm/refinement_stepper.py` `FixedPatchStepper.__init__` |
+| Checkpoint with Jets | refused | `simulation.py` `Simulation.save_checkpoint` |
 
 Raw exchange is the cut-link momentum reaction (wall + aperture), not a validated
 nozzle thrust or stress load. Jet amplitude is a lattice velocity, not a flow rate.

src/CelerisLab/lbm/refinement_stepper.py

@@ -949,8 +949,8 @@ class FixedPatchStepper:
             if exc[0] is None:
                 raise
 
-    # Read-only compatibility views over the level lists. Internal code must not use them;
-    # REMOVE AFTER the existing tests/docs migrate to hierarchy/_layouts/_level_* lists.
+    # Read-only compatibility views over the level lists, kept on purpose for the existing
+    # tests and docs. Internal code must not use them; it reads hierarchy/_layouts/_level_*.
     patch = property(lambda self: self.hierarchy.pairs[0])
     child_patch = property(lambda self: self.hierarchy.pairs[1] if self.hierarchy.depth > 2 else None)
     base_layout = property(lambda self: self._layouts[0])