Add Graph+Debug support for Compute

[Kyle-Ye]

Solve #197 (comment)

cc @jcmosc

[augmentcode]

🤖 Augment PR Summary

Summary: Re-enables Graph+Debug on Darwin for OPENATTRIBUTEGRAPH_COMPUTE builds by supplying missing Graph.descriptionFormat* constants.

Why: Aligns Compute’s description option values with the shims API so dict/dot graph descriptions can be requested consistently across vendors.

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[augmentcode]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 32.08%. Comparing base (2682d4b) to head (478f4e7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #221       +/-   ##
===========================================
+ Coverage   16.88%   32.08%   +15.19%     
===========================================
  Files          72       70        -2     
  Lines        4897     2596     -2301     
===========================================
+ Hits          827      833        +6     
+ Misses       4070     1763     -2307     

Flag	Coverage Δ
ios	32.10% <ø> (+15.20%)	⬆️
macos	9.95% <ø> (+6.46%)	⬆️
ubuntu	11.79% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
Sources/OpenAttributeGraphShims/Graph+Debug.swift	0.00% <ø> (ø)

... and 35 files with indirect coverage changes

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