View state: hide, show and isolate viewport items, saved with the model

view.hide, view.show, view.isolate and view.show_all change which
bodies, surfaces, datums, boundary conditions, loads, reference points
and couplings the viewport draws. The hidden items are view state: the
manifest's `view` keeps them, a change marks the model unsaved, but it
is neither journalled nor undone and leaves results current. Items that
go away are forgotten. Headless pictures leave hidden items out; the
glyph builders take a filter. Tools > View > Show All claims the
commands.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

docs/formats/fieldcraft.md

@@ -12,8 +12,8 @@ unzip tool reads them: `unzip -p bracket.fieldcraft model.json`):
 
 | Part | Content |
 |---|---|
-| `fieldcraft.json` | Manifest: `format` (`"fieldcraft/1"`), `generator` (`"FieldCraft 0.5.8"`), `geometry`, and `parts`: the byte size and SHA-256 of each other part. |
-| `model.json` | The model definition: unit system, sets, materials, sections, reference points, couplings, boundary conditions, loads, steps, datum planes and axes, and the partitions that cut the geometry (in order; applied again when the design is opened). Pretty-printed JSON with a fixed key order (maps sorted by name), so a change shows as a line diff. Its form is the model's own JSON form, which commands take as parameters. |
+| `fieldcraft.json` | Manifest: `format` (`"fieldcraft/1"`), `generator` (`"FieldCraft 0.5.8"`), `geometry`, `view` (left out when empty), and `parts`: the byte size and SHA-256 of each other part. |
+| `model.json` | The model definition: unit system, sets, materials, sections, reference points, couplings, boundary conditions, loads, steps, datum planes, axes and points, and the partitions that cut the geometry (in order; applied again when the design is opened). Pretty-printed JSON with a fixed key order (maps sorted by name), so a change shows as a line diff. Its form is the model's own JSON form, which commands take as parameters. |
 | `mesh.bin` | Nodes, elements and geometry tags, binary (below). |
 | `journal.json` | The commands that built the model, `[{"command": id, "params": {...}}, ...]`, one per line. It is a script `fieldcraft-cli run` replays. |
 
@@ -40,6 +40,10 @@ is reported as a warning and the model still opens; sets bind to geometry names,
 brings the mesh in line with a changed design. A geometry file that could not be opened keeps its
 reference, so saving again does not lose it.
 
+`view` is view state, not part of the definition: the items the viewport hides (`view.hide`,
+`view.isolate`), as `{"hidden": [{"kind": "datum", "name": "Sym"}, …]}` with `kind` one of
+`body`, `surface`, `datum`, `boundary_condition`, `load`, `reference_point`, `coupling`.
+
 ## `mesh.bin`
 
 Little-endian: