Make attribute label, description, and value optional with auto-label generation + add unit tests

[Copilot]

label, description, and value were required positional arguments on all attribute constructors, forcing verbose boilerplate even when defaults were sufficient. This PR makes all three optional and adds tests validating the behavior.

Description

All attribute descriptor constructors (File, BoolParam, IntParam, FloatParam, StringParam, ColorParam, PushButtonParam, ChoiceParam, ListAttribute, GroupAttribute, and geometry variants) now accept name as the only required argument.

Before:

desc.File(name="outputFile", label="Output File", description="", value=None)
desc.IntParam(name="frameCount", label="Frame Count", description="", value=0, range=(0, 1000, 1))

After:

desc.File(name="outputFile")          # label="Output File", description="", isDynamicValue=True as output
desc.IntParam(name="frameCount", range=(0, 1000, 1))  # label="Frame Count", description="", value=0 as input

Features list

• label=None on all attribute constructors — auto-generated from the name via convertToLabel() (camelCase → "Camel Case", snake_case → "Snake Case", acronyms preserved: useGPU → "Use GPU")
• description=None on all attribute constructors — defaults to ""
• value=None on all typed param constructors — when used as an output, the attribute is isDynamicValue=True (value computed at runtime); when used as an input, the runtime value is the type's zero-value (str()→"", int()→0, float()→0.0, bool()→False)
• Fix mutable default values=[] in ChoiceParam → values=None
• convertToLabel(name) added to desc/attribute.py (mirrors existing implementation in bin/meshroom_newNodeType)
• Unit tests in tests/test_attributeDescDefaults.py covering minimal creation for all types, isDynamicValue on descriptors, input type defaults at runtime, and output None values before computation

Implementation remarks

getDefaultValue() in meshroom/core/attribute.py was extended: when desc.value is None, the attribute is an input, and _valueType is not None, it returns _valueType() instead of None. This gives typed inputs a sensible default without requiring node authors to specify it explicitly.

ListAttribute and GroupAttribute always initialize with value=[] / value={} internally, so they remain isDynamicValue=False regardless.

Param.__init__ retains positional-style signature internally; the optional defaults are applied at each concrete subclass level and propagate upward.

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[codecov]

Codecov Report

❌ Patch coverage is 95.74468% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.36%. Comparing base (9ccb5e5) to head (e938a1d).
⚠️ Report is 18 commits behind head on develop.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
meshroom/core/desc/attribute.py	90.69%	4 Missing ⚠️
tests/test_attributeDescDefaults.py	97.84%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3042      +/-   ##
===========================================
+ Coverage    83.05%   83.36%   +0.30%     
===========================================
  Files           72       73       +1     
  Lines         9657     9843     +186     
===========================================
+ Hits          8021     8206     +185     
- Misses        1636     1637       +1     

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