Make package init cross-platform: fix Windows-only APIs and add configurable bin path suffix

[Copilot]

The package init in utils.py used os.add_dll_directory (Windows-only) unconditionally and hardcoded ";" as the PATH separator, breaking on Linux/macOS. The bin folder suffix (bin/x64) was also hardcoded with no env var override, unlike the install root.

Changes

• os.add_dll_directory: Guarded all call sites with sys.platform == "win32"; returns None on other platforms
• PATH separator: Replaced hardcoded ";" with os.pathsep in _update_python_env_path and _try_mike_install_bin_setup
• Configurable bin path suffix: The MIKEPLUSPY_INSTALL_BIN environment variable is resolved at the call site in __init__.py and passed directly as bin_path, mirroring how MIKEPLUSPY_INSTALL_ROOT works for the install root

# Override the bin folder suffix (relative path, e.g. for a different architecture)
os.environ["MIKEPLUSPY_INSTALL_BIN"] = "bin/arm64"
import mikeplus

• Warning messages: Added helpful warnings for all possible outcomes in setup_bin_path:
  • When a custom install root env var is set, warns with the resolved path and bin directory being used
  • When DHI.Mike.Install auto-detection fails, warns with the exception detail before falling back
  • When the default fallback path is used, the existing warning is retained
  • When the custom bin path does not exist, the FileNotFoundError includes the env var name, its value, and a hint to unset it for auto-detection

Original prompt

The package init sets up both the Python and .NET environments to find assemblies and native libraries. Fix it to be cross platform (e.g. os.add_dll_directory is windows only), and make the bin folder suffix configurable the same way as the MIKE+ install root is.

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[ryan-kipawa]

Combine this with the line above to just check that environment variable, and if not, pass the default. No need to pass the env variable name.

[Copilot]

Done in 8dd2f5a. The MIKEPLUSPY_INSTALL_BIN env var is now resolved at the call site via os.getenv("MIKEPLUSPY_INSTALL_BIN", "bin/x64"), and the env_var_name_bin_path parameter has been removed from setup_bin_path.

[ryan-kipawa]

Review this entire method to ensure it's functioning as intended. There should be helpful warning messages to the user to all possible outcomes that let them take corrective action.

[Copilot]

Addressed in 8dd2f5a. Added warning messages for all outcomes:

• Custom install root used: warns with the resolved path so the user can verify it's correct.
• DHI.Mike.Install auto-detection fails: warns with the exception message so the user knows why, and that it's falling back.
• Falling back to default path: existing warning already in place, kept as-is.
• Custom path not found: FileNotFoundError now includes the env var name, its value, and a hint to unset it for auto-detection.