In `@newton/_src/usd/__init__.py`:
- Around line 16-19: Remove the unnecessary noqa comment from the side-effect
import in newton/_src/usd/__init__.py: keep the import newton_usd_schemas (to
register the Newton schema plugin) but delete the trailing "# noqa: F401" so the
linter no longer reports an unused directive; ensure the from pxr import Usd
line remains unchanged.

In `@newton/_src/utils/import_usd.py`:
- Around line 942-947: The code currently computes physics_dt by dividing 1.0 by
the value returned from R.get_value for key "time_steps_per_second" which can be
None or <= 0; update the logic around the R.get_value call that reads
time_steps_per_second (used to compute physics_dt) to guard against None or
non-positive values: capture the raw value into a local (e.g.,
time_steps_per_second_raw), if it is None or <= 0 replace it with a sensible
fallback (for example 60.0 or another project default) and optionally emit a
warning when verbose is true, then compute physics_dt = 1.0 /
time_steps_per_second_safe; ensure you reference physics_scene_prim and
PrimType.SCENE in the same block so behavior remains unchanged when a valid
value exists.

In `@newton/tests/test_schema_resolver.py`:
- Around line 1339-1383: The test test_max_hull_vertices assumes that when
resolver priority is [SchemaResolverPhysx(), SchemaResolverNewton()] the
resolved max_hull_vertices will be Newton's sentinel (-1/32), but PhysX
currently wins and yields 64; update the failing assertion in
test_max_hull_vertices (the assertion after creating the
physxConvexHullCollision:hullVertexLimit attribute) to expect 64, or
alternatively change the resolver order to [SchemaResolverNewton(),
SchemaResolverPhysx()] if you intend Newton to override; locate the check via
the test name and the SchemaResolverManager([SchemaResolverPhysx(),
SchemaResolverNewton()]) usage and adjust the assertion accordingly.
- Around line 1286-1338: The test test_contact_margin currently expects None but
the resolver returns the unset sentinel (-inf); update the assertion to expect
the sentinel instead (e.g. assertEqual(contact_margin, float("-inf"))) at the
call to resolver.get_value in test_contact_margin, or alternatively call
resolver.get_value with an explicit default if supported; locate the failing
line by searching for test_contact_margin and the resolver.get_value(collider,
PrimType.SHAPE, "contact_margin") invocation and replace the
assertEqual(contact_margin, None) with an assertion for float("-inf") (or pass a
default value to get_value).

In `@newton/_src/usd/__init__.py`:
- Around line 16-21: The import line "import newton_usd_schemas  # noqa: F401"
contains an unnecessary noqa suppressor; remove the trailing "# noqa: F401" so
Ruff RUF100 is satisfied and keep the import as-is (inside the try/except that
sets Usd = None on ImportError) so the module registration via import
newton_usd_schemas still occurs and the Usd symbol from "from pxr import Usd"
remains handled in the except block.

In `@newton/_src/utils/import_usd.py`:
- Around line 941-946: The computation of physics_dt uses 1.0 / R.get_value(...)
which can raise ZeroDivisionError or TypeError if time_steps_per_second is 0 or
None; update the logic around the call that sets physics_dt (and related call to
R.get_value with physics_scene_prim and PrimType.SCENE) to first fetch the raw
value into a local (e.g., time_steps_per_second_value), validate it (not None
and not 0), and only then compute physics_dt = 1.0 / value, otherwise use a safe
fallback default (or log/raise a clear error); similarly ensure gravity_enabled
read remains bool by coercing or defaulting when R.get_value returns None.

In `@newton/tests/test_import_usd.py`:
- Around line 2966-3168: The test file contains unused "# noqa: PLC0415" markers
on pxr import lines (e.g. the imports in test_contact_margin_parsing,
test_scene_gravity_enabled_parsing, test_scene_time_steps_per_second_parsing,
test_scene_max_solver_iterations_parsing and the earlier test that imports
UsdShade) which Ruff flags as RUF100; remove those trailing "# noqa: PLC0415"
comments from the relevant import statements (the lines starting with "from pxr
import Usd, UsdGeom, UsdPhysics" and "from pxr import Usd, UsdGeom, UsdPhysics,
UsdShade") so the imports remain but the unused noqa markers are deleted.

In `@newton/tests/test_schema_resolver.py`:
- Around line 1286-1338: The test incorrectly expects None when
SchemaResolverPhysx is first in the SchemaResolverManager; change the assertion
after creating resolver = SchemaResolverManager([SchemaResolverPhysx(),
SchemaResolverNewton()]) in test_contact_margin so it expects PhysX's mapping
default (negative infinity) instead of None—i.e., assert that
resolver.get_value(collider, PrimType.SHAPE, "contact_margin") equals
float("-inf") (or use an equivalent is-inf negative check).
- Around line 1339-1383: The test's initial expectation is wrong: when resolver
= SchemaResolverManager([SchemaResolverPhysx(), SchemaResolverNewton()]) the
PhysX mapping default for max_hull_vertices is 64, so update the assertion after
calling resolver.get_value(collider, PrimType.SHAPE, "max_hull_vertices") in
test_max_hull_vertices to expect 64 instead of -1; leave the subsequent explicit
sets and other resolver-order assertions unchanged.

In `@newton/_src/utils/import_usd.py`:
- Around line 36-37: Uncomment and restore the public re-export of
SchemaResolverNewton (and the other schema resolver classes) so users can pass
instances to parse_usd via the schema_resolvers parameter: locate the commented
import and export lines for SchemaResolverNewton in the module that exposes the
public USD API, re-enable the import from ..usd.schemas (SchemaResolverNewton)
and add it to the module's exports (e.g., __all__ or explicit export list) so
SchemaResolverNewton is available to callers of parse_usd and documented as part
of the public API.

In `@newton/_src/utils/import_usd.py`:
- Around line 1419-1425: get_value can return None when schema resolvers are
disabled, so in the contact_margin handling (around R.get_value(...,
prim_type=PrimType.SHAPE, key="contact_margin")), treat None the same as the
unset sentinel float("-inf") and fallback to
builder.default_shape_cfg.contact_margin; update the contact_margin assignment
logic in the block using R.get_value and also the similar occurrence around line
1445 to check for contact_margin is None || contact_margin == float("-inf") and
then set contact_margin = builder.default_shape_cfg.contact_margin so downstream
ShapeConfig receives a numeric value.