Fix tomli compatibility issue for older Python version

[AlirezaShamsoshoara]

This PR addressing this issue: issue284

Summary

Fixes a ModuleNotFoundError when running OpenEnv CLI commands on Python 3.10 and older by adding a fallback import for the tomli package.

Problem

The tomllib module is only available in Python 3.11+. When running on Python 3.10 and older, the following error occurs:

$ openenv push
Traceback (most recent call last):
  ...
  File "/src/openenv/cli/_validation.py", line 15, in <module>
    import tomllib
ModuleNotFoundError: No module named 'tomllib'

Solution

Add a try/except import that falls back to tomli (the third-party backport) when tomllib is not available:

try:
    import tomllib
except ModuleNotFoundError:
    import tomli as tomllib

Changes

• src/openenv/cli/_validation.py: Updated import to support Python 3.10 and older

[Darktex]

Summary

This PR fixes a ModuleNotFoundError when running OpenEnv CLI commands on Python 3.10 and older by adding a fallback import for the tomli package.

Overall Assessment: Simple, correct fix. Ready to merge.

Analysis

The fix is correct. tomllib was added to Python's standard library in Python 3.11, but the project's pyproject.toml specifies requires-python = ">=3.10". The tomli package is already listed as a dependency (tomli>=2.3.0), so this import fallback works correctly.

Aspect	Assessment
Pattern used	Standard Python compatibility pattern
Dependency already exists	Yes (tomli>=2.3.0 in pyproject.toml)
API compatibility	Yes (tomli has identical API to tomllib)

Note

PR #285 also includes this same fix (duplicated). Consider merging this PR first or letting it be included in PR #285.

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Reviewed by Claude

[Darktex]

Easy approval!