fix(binder): prevent duplicate reservation pods for a single gpu-group (#1693) [v0.12]

[gshaibi]

Description

Backport of #1693 to the v0.12 release branch.

At scale with fractional GPU workloads, multiple GPU reservation pods could be created for a single runai-gpu-group on a node, each reserving a different physical GPU. Since the scheduler tracks fractional-GPU capacity by gpu-group, a group spanning two devices corrupts accounting — affected GPUs appear full, fractional pods stay pending, and the state does not self-correct.

Fix: reservation pods are named deterministically per (node, gpu-group) (hashed) and AlreadyExists on create is treated as success (reuse the existing pod), so concurrent, retried, and multi-replica creates collide on a single API-server object instead of duplicating. Existing reservation pods (old random-suffix names) are unaffected — they are still resolved by gpu-group label, so no migration is needed.

Related Issues

Fixes #1673

Checklist

• Self-reviewed
• Added/updated tests (if needed)
• Updated documentation (if needed)

Breaking Changes

None.

Additional Notes

Cherry-pick of 73298061 from #1693 onto v0.12 (manual adjustments limited to conflict resolution: dropping the unused rand import and placing the new test / changelog entry into this branch's layout). Verified locally on v0.12: go build, go vet, gofmt, and the resourcereservation package tests (including the new duplicate-gpu-group race test) pass.

🤖 Generated with Claude Code

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