Make cim-graph and gridappsd-python optional dependencies

[Copilot]

• Identified root cause: cim-graph==0.4.1a2 and gridappsd-python==2025.3.2a13 are pre-release packages listed as core dependencies
• Moved cim-graph and gridappsd-python to [project.optional-dependencies] cim extra in pyproject.toml
• Updated uv.lock to reflect dependency changes
• Improved error handling in api.py for missing CIM dependencies
• Added tests/cim_converter/conftest.py to skip CIM tests when optional extra not installed
• Updated README to document:
  • Optional extras table with pip install distopf[cim]
  • Note explaining why pre-release packages are optional
  • Developer install command for the [cim] extra
  • New "CIM XML Interface" section with usage example and error message guidance

Original prompt

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This section details on the original issue you should resolve

<issue_title>gridappsd-python<2025.3.2a1 is available and distopf==0.3.1 depends on gridappsd-python>=2025.3.2a1</issue_title>
<issue_description>pre-release issue when building

tylor@WE48962:~/dev/MultiEntityTestBed$ uv run python examples/single_entity.py
× No solution found when resolving dependencies for split (python_full_version >= '3.12'):
╰─▶ Because only gridappsd-python<2025.3.2a1 is available and distopf==0.3.1 depends on gridappsd-python>=2025.3.2a1, we can conclude that distopf==0.3.1 cannot be used.
And because only distopf<=0.3.1 is available and your project depends on distopf>=0.3.1, we can conclude that your project's requirements are unsatisfiable.</issue_description>

<agent_instructions>Determine if this has been fixed.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes gridappsd-python<2025.3.2a1 is available and distopf==0.3.1 depends on gridappsd-python>=2025.3.2a1 #1

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[nathantgray]

@copilot ensure that the readme properly documents the install requirements

[Copilot]

@copilot ensure that the readme properly documents the install requirements

Updated in commit baa5771. The README now includes:

• An Optional Extras table under Installation showing pip install distopf[cim] with an explanation that the cim extra depends on pre-release packages
• The developer install command for the [cim] extra (pip install -e ".[cim]")
• A new CIM XML Interface section showing how to use CIM file import and what error to expect if the extra isn't installed