[NEWTON] Replaces omni.client with isaaclab implementation of client

[ooctipus]

Description

This PR replaces omni.client with light weight implementation of isaaclab.utils.client.
Fixes # (issue)

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Greptile Overview

Greptile Summary

This PR replaces omni.client with a lightweight isaaclab implementation (isaaclab.utils.client) that supports local files, HTTP/HTTPS URLs, and S3 paths. The new client provides essential functionality: path normalization, stat/read operations, file copying, and USD dependency resolution.

Key Changes

• New client module (source/isaaclab/isaaclab/utils/client.py): 574 lines implementing stat(), read_file(), copy(), and USD reference downloading
• Updated asset utilities to use new client for cloud storage access and USD dependency management
• Simplified file spawning logic in from_files.py by removing version-specific path fallback logic
• Added boto3/botocore dependencies for S3 support
• Removed omni.client dependency across the codebase

Issues Found

• Critical: S3 client initialized at module import (line 64 of client.py) will fail in environments without AWS credentials
• Critical: Event loop creation in download_usd_with_references_sync() (line 567) can conflict with existing event loops

Recommendation

The migration is well-structured but needs the two critical issues fixed before merge to avoid runtime failures in certain environments.

Confidence Score: 3/5

• This PR has critical issues that will cause runtime failures in certain environments and should not be merged without fixes.
• Score of 3 reflects that while the overall architecture and migration approach is sound, there are two critical bugs in the new client implementation that will cause failures: (1) S3 client initialization at import time without credentials handling, and (2) unsafe event loop creation that can conflict with existing loops. These issues need to be resolved before merging.
• Pay close attention to source/isaaclab/isaaclab/utils/client.py - contains critical bugs that need fixing

Important Files Changed

File Analysis

Filename	Score	Overview
source/isaaclab/isaaclab/utils/client.py	3/5	New lightweight client implementation replacing omni.client with support for local/HTTP/S3 access. Has critical issue with S3 client initialization and event loop handling that needs fixing.
source/isaaclab/isaaclab/utils/assets.py	4/5	Updated to use new client module instead of omni.client. Implements USD dependency downloading and cloud asset retrieval. Clean migration with proper error handling.
source/isaaclab/isaaclab/sim/spawners/from_files/from_files.py	5/5	Simplified USD file path checking logic to use new check_file_path and retrieve_file_path utilities. Cleaner implementation than before.

Sequence Diagram

sequenceDiagram
    participant User as User Code
    participant Spawner as from_files.py
    participant Assets as assets.py
    participant Client as client.py
    participant Storage as Cloud Storage (S3/HTTP)
    participant USD as USD Layer (pxr.Sdf)

    User->>Spawner: spawn_from_usd(prim_path, usd_path, cfg)
    Spawner->>Assets: check_file_path(usd_path)
    Assets->>Client: stat(usd_path)
    
    alt Local file
        Client-->>Assets: Result.OK (status=1)
        Assets-->>Spawner: 1 (local)
    else Remote file (HTTP/S3)
        Client->>Storage: HEAD request / head_object()
        Storage-->>Client: metadata
        Client-->>Assets: Result.OK (status=2)
        Assets-->>Spawner: 2 (remote)
        
        Spawner->>Assets: retrieve_file_path(usd_path)
        
        alt USD file
            Assets->>Client: download_usd_with_references_sync()
            Client->>Storage: download root USD
            Storage-->>Client: USD file
            Client->>USD: _find_usd_references(local_path)
            USD-->>Client: list of referenced assets
            
            loop For each reference
                Client->>Storage: download referenced asset
                Storage-->>Client: asset file
                alt Reference is USD
                    Client->>USD: _find_usd_references()
                    USD-->>Client: nested references
                end
            end
            
            Client-->>Assets: mapping{remote_url: local_path}
            Assets-->>Spawner: local_usd_path
        else Non-USD file
            Assets->>Client: copy(url, local_path)
            Client->>Storage: download file
            Storage-->>Client: file data
            Client-->>Assets: Result.OK
            Assets-->>Spawner: local_file_path
        end
    else File not found
        Client-->>Assets: Result.ERROR_NOT_FOUND (status=0)
        Assets-->>Spawner: 0 (not found)
        Spawner-->>User: FileNotFoundError
    end
    
    Spawner->>Spawner: create_prim(prim_path, usd_path)
    Spawner-->>User: prim

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[greptile-apps]

_{6 files reviewed, 2 comments}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

logic: boto3 client initialized at module import without configuration. This may fail in environments without AWS credentials or when custom S3 endpoints are needed (like LocalStack).

Suggested change

	_s3 = boto3.client("s3")
	# Initialize S3 client lazily to allow configuration
	_s3 = None
	def _get_s3_client():
	global _s3
	if _s3 is None:
	_s3 = boto3.client("s3")
	return _s3

[kellyguo11]

keeping this one on hold for now in favor of omni.client