Add pathlib-based file existence utilities

[Copilot]

Adds Python-native file existence checking utilities using pathlib.Path.exists() as an alternative to platform-specific implementations.

Changes

• qumat/file_utils.py: New module with two utilities:

  • path_exists(file_path): Returns boolean for file/directory existence
  • ensure_file_exists(file_path): Returns Path object or raises FileNotFoundError
  • Both accept string or Path inputs

• qumat/__init__.py: Exports new utilities for direct import from qumat package

• testing/test_file_utils.py: 10 test cases covering existence checks, type handling, and cross-platform paths

• examples/file_utils_example.py: Usage demonstration

Usage

from qumat import path_exists, ensure_file_exists
from pathlib import Path

# Check existence
if path_exists("/path/to/file.txt"):
    process_file()

# Verify and get Path object
try:
    config_path = ensure_file_exists("config.yaml")
except FileNotFoundError:
    use_defaults()

# Works with Path objects
path_exists(Path.home() / "data.csv")

Original prompt

// Verify file exists
if !path.exists() {
Contributor
@rich7420
rich7420
yesterday
I think we could add this path.exists() in other format.

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[ryankert01]

@copilot we've change base branch to dev-qdp

[Copilot]

@copilot we've change base branch to dev-qdp

Acknowledged. The PR is now targeting dev-qdp and is mergeable with no conflicts.