fix(deps): bump usd-core to >=26.5 for multithreaded collider crash fix

[pv-nvidia]

Description

Bumps the kit-less usd-core pin from >=25.11,<26.0 to >=26.5,<27.0.

OpenUSD 26.05 fixes a race in UsdPhysicsParsingUtility
(LoadUsdPhysicsFromRange → _FinalizeCollisionDescs) that corrupts the heap
(malloc_consolidate(): invalid chunk size / double free) when parsing a
single rigid body with many mesh colliders beneath it — e.g. the H2 robot on
the Newton tablecloth workload — before the first simulation step.

• Fix: OpenUSD PR Isaac-Velocity-Flat-Spot-v0 #4002 / commit 060715f ("[usdPhysics] fix for a multithreaded
  crash if one rigidbody has multiple colliders beneath"), by Paul Molodowitch.
  First released in OpenUSD 26.05 (= usd-core 26.5). 26.03 was tagged 2 days
  before the fix, so it does not contain it.
• Empirically verified: usd-core 25.11 / 26.3 crash; 26.5 clean (400
  multithreaded parses, 0 crashes). Interim workaround PXR_WORK_THREAD_LIMIT=1
  is not 100% reliable.

⚠️ Known blocker (this is a CI experiment / draft)

The previous <26.0 cap was added by @AntoineRichard in #6165 because the Isaac
Sim runtime stack loads USD 25.x internals, so a kit-less usd-core 26.5 causes
an ABI mismatch. This PR therefore likely cannot pass install/smoke CI until
the Isaac Sim runtime's bundled OpenUSD is uplifted to ≥26.05 (or PR #4002 is
backported). Opened as a draft to surface exactly what CI does with the bump.

cc @AntoineRichard @kellyguo11 @ooctipus

Type of change

• Bug fix (dependency / ABI)

Checklist

• Updated the metadata guard test (test_source_package_metadata.py)
• Added a changelog fragment
• Pre-commit hooks pass

[greptile-apps]

Greptile Summary

Bumps the kit-less usd-core dependency pin from >=25.11,<26.0 to >=26.5,<27.0 to pick up the OpenUSD 26.05 fix for a multithreaded heap-corruption crash in UsdPhysicsParsingUtility (OpenUSD PR #4002). The PR description explicitly flags that this bump is a known draft/experiment because the Isaac Sim runtime bundles USD 25.x, so installing usd-core 26.5 alongside it causes an ABI mismatch that will break CI until the runtime is uplifted.

• pyproject.toml: single-line dependency version constraint change (usd-core, x86_64/AMD64 only).
• test_source_package_metadata.py: test renamed and assertion updated to match the new pin exactly.
• Changelog fragment added as .major.rst, correctly labelled Breaking.

Confidence Score: 4/5

Safe to merge as a draft experiment; the ABI mismatch with Isaac Sim's bundled USD 25.x is a self-documented blocker that will surface immediately in CI.

The change is minimal and internally consistent — pyproject.toml, the guard test, and the changelog all agree on the new range. The only material risk is the known ABI incompatibility between usd-core 26.x and the Isaac Sim runtime's bundled USD 25.x, which the PR author explicitly acknowledges and uses as the reason this is opened as a draft. No logic, data, or security issues were introduced by the three changed files themselves.

source/isaaclab/pyproject.toml — the version constraint is the single load-bearing line; confirm the upper bound <27.0 is intentional and won't need tightening once 27.x is released.

Important Files Changed

Filename	Overview
source/isaaclab/pyproject.toml	Bumps usd-core pin from >=25.11,<26.0 to >=26.5,<27.0 to include the OpenUSD 26.05 multithreaded physics parser crash fix; the author acknowledges this breaks ABI compatibility with the Isaac Sim runtime's bundled USD 25.x.
source/isaaclab/test/cli/test_source_package_metadata.py	Test renamed and assertion updated to match the new usd-core pin; change is consistent with pyproject.toml.
source/isaaclab/changelog.d/pverswyvelen-usd-2605-collider-crash-fix.major.rst	New changelog fragment accurately documenting the breaking version bump and the upstream OpenUSD crash it fixes.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant User as Kit-less install
    participant Pip as pip resolver
    participant USD as usd-core 26.5
    participant ISim as Isaac Sim runtime (USD 25.x)

    User->>Pip: install isaaclab[kit-less]
    Pip->>USD: "resolve usd-core>=26.5,<27.0"
    USD-->>Pip: usd-core 26.5 (OpenUSD 26.05 ABI)
    Pip-->>User: installed

    Note over ISim: Isaac Sim runtime bundles USD 25.x (unchanged)
    User->>ISim: launch with Isaac Sim
    ISim-->>User: ABI mismatch (26.x vs 25.x) - CI blocker acknowledged in PR

    User->>USD: parse USD physics (kit-less / standalone)
    USD-->>User: "thread-safe parse (OpenUSD PR #4002 fix present)"

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sequenceDiagram
    participant User as Kit-less install
    participant Pip as pip resolver
    participant USD as usd-core 26.5
    participant ISim as Isaac Sim runtime (USD 25.x)

    User->>Pip: install isaaclab[kit-less]
    Pip->>USD: "resolve usd-core>=26.5,<27.0"
    USD-->>Pip: usd-core 26.5 (OpenUSD 26.05 ABI)
    Pip-->>User: installed

    Note over ISim: Isaac Sim runtime bundles USD 25.x (unchanged)
    User->>ISim: launch with Isaac Sim
    ISim-->>User: ABI mismatch (26.x vs 25.x) - CI blocker acknowledged in PR

    User->>USD: parse USD physics (kit-less / standalone)
    USD-->>User: "thread-safe parse (OpenUSD PR #4002 fix present)"

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