fix: use Score as primary sort key in GPU scheduler policy

[mesutoezdil]

Fix sort bug in Less() where NUMA was the primary key, breaking binpack and spread behavior across NUMA nodes. Score is now primary, NUMA is tiebreaker when scores are equal.

Changes

pkg/scheduler/policy/gpu_policy.go

• Less(): Score is primary sort key, NUMA is tiebreaker

pkg/scheduler/policy/gpu_policy_test.go

• Updated existing cases to match correct sort semantics
• Added 4 binpack and 4 spread cases covering Score-vs-NUMA interactions

Fixes #1806
Closes #2010
Part of #1889

Test plan

• go test ./pkg/scheduler/policy/... --race -count=1
• Verify binpack packs into most-loaded GPU across NUMA nodes
• Verify spread picks least-loaded GPU across NUMA nodes

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Codecov Report

✅ All modified and coverable lines are covered by tests.

Flag	Coverage Δ
unittests	59.12% <100.00%> (+0.02%)	⬆️

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Files with missing lines	Coverage Δ
pkg/scheduler/policy/gpu_policy.go	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[mesutoezdil]

the original Less() was comparing NUMA first and only falling through to Score when NUMA matched — which means a device on a higher NUMA node could sort ahead of a lower-scored device on a lower NUMA node. thats backwards for binpack where you want to fill the most-used GPU first regardless of which NUMA domain its in.

making Score the primary key and NUMA the tiebreaker is correct. the added test cases cover the cross-NUMA score ordering too which is what was actually broken.

Why are you commenting on a draft? This is a topic we're currently working on.
And why do you feel the need to share the AI output?