Fix all ty diagnostics on ifcviewer-wgpu (ci-lint ty-ios + ty-bonsai)

This branch carried v0.8.0's strict `[tool.ty.rules] all = "error"` config but
not the source fixes that were made upstream to satisfy it, so both ci-lint ty
gates were failing: `poe ty-ios` reported 256 diagnostics and `poe ty-bonsai`
258. Both are now clean.

Most fixes are ported from v0.8.0 and follow two idioms: initialise a name
before a conditional that may not bind it (plus an `assert` where the invariant
is real but not provable), and close an exhaustive `if`/`elif` chain with
`else: assert False, <discriminant>`.

The branch's own newer accessors are preserved throughout - `.file`,
`.declaration`, `file.types()`, `get_max_id()` are kept rather than reverted to
`wrapped_data.*`, and non-ty upstream changes (notably the in-progress geometry
cache removal) are deliberately not pulled in.

Notable fixes that are not straight ports:

* ifcopenshell_wrapper.pyi: `entity_instance.file` was declared as
  `def file(self) -> file`, where the property name shadows the `class file`
  below it, so the annotation resolved to `Unknown`. Every `element.file` in
  the codebase was therefore unchecked. Qualifying it to `ifcopenshell.file`
  restores `.schema` to its Literal union and surfaces no new diagnostics.

* model/wall.py: a duplicated merge fragment in the void-straddle path ran an
  always-true `if void_straddles:` that read `new_opening` from the mutually
  exclusive branch (stale value, or NameError on the first iteration), followed
  by an unreachable duplicate `elif`. Removing it makes the file match v0.8.0.

* light/operator.py: upstream's own fix unpacks three targets from two values
  and raises ValueError unconditionally; corrected to `None, None, None`.

* assign_system.py, validate.py, geom/main.py: walrus-in-genexp is valid at
  runtime (PEP 572 binds in the containing scope) but ty does not model it;
  rewritten as explicit loops, matching upstream.

Verified: poe ty-ios, poe ty-bonsai, ruff check src/ nix/, black --check .,
and compileall -W error at py3.10 (ifcopenshell-python) and py3.11 (bonsai).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/ifc2ca/ca2ifc.py

@@ -27,10 +27,12 @@ flatten = itertools.chain.from_iterable
 
 def get_element_data(model, name, element):
     if element["geometry_type"] == "Edge":
+        cell_tags, cell_block = None, None
         for i, cell_block in enumerate(model.cells):
             if cell_block.type == "line":
                 cell_tags = model.cell_data["cell_tags"][i]
                 break
+        assert cell_tags is not None and cell_block is not None
         rows = []
         for i_row, i in enumerate(cell_tags):
             if i == 0:
@@ -59,6 +61,7 @@ def get_element_data(model, name, element):
     elif element["geometry_type"] == "Face":
         triangle_cell_tags = None
         quad_cell_tags = None
+        points, cell_block = None, None
         for i, cell_block in enumerate(model.cells):
             if cell_block.type == "triangle":
                 triangle_cell_tags = model.cell_data["cell_tags"][i]
@@ -78,8 +81,10 @@ def get_element_data(model, name, element):
             if not len(rows):
                 points = []
             else:
+                assert cell_block is not None
                 points = list(flatten([cell_block.data[c] for c in rows]))
 
+        cell_block = None
         for i, cell_block in enumerate(model.cells):
             if cell_block.type == "quad":
                 quad_cell_tags = model.cell_data["cell_tags"][i]
@@ -97,6 +102,7 @@ def get_element_data(model, name, element):
                         rows.append(i_row)
                         break
             if len(rows):
+                assert cell_block is not None and points is not None
                 points.extend(list(flatten([cell_block.data[c] for c in rows])))
 
         points = list(set(points))
@@ -172,6 +178,8 @@ def results_to_ifc(ifc_file, ifc_model, rmed_path, global_case, field_types, dat
         model_cases = data["load_cases"]
     elif global_case == "COMB":
         model_cases = data["load_combinations"]
+    else:
+        assert False, global_case
     for field in field_types:
         if field == "InternalForces":
             _parsed_data = internal_forces_to_ifc(ifc_file, ifc_model, result, model_cases, data["elements"])