fix: keep A10 GRID on the v19 LTS branch

[Ganeshkumar Ashokavardhanan (ganeshkumarashok)]

Summary

Restore a security-patched R580/vGPU 19.6 LTS option for A10 instead of publishing R595 through both GRID image variants.

• grid / aks-gpu-grid: 580.178.04, using Azure's official vGPU 19.6 installer.
• grid_v20 / aks-gpu-grid-v20: 595.91.07, unchanged.
• CUDA and CUDA-LTS images and driver selection are unchanged.
• Update both GRID variants within their configured branches. Read the upstream JSON's actual Latest/Archive arrays and Drivers field, select the highest numeric version in the requested branch, and fail rather than switch branches, downgrade, or accept a mismatched installer URL.
• Add ten updater/config regression tests to CI and document the compatibility and consumer-release boundary.

Related: #195. This is the producer change, not a completed AKS node-image rollout.

Compatibility basis

Azure's Linux GRID support matrix lists:

SKU family	Documented GRID options
NVadsA10_v5	vGPU 19.6 LTS and vGPU 20.2
NCv6 RTX PRO 6000 BSE	vGPU 20.2
NCasT4_v3	vGPU 20.2

AgentBaker already separates its A10 GRID path (aks-gpu-grid) from NCv6 (aks-gpu-grid-v20). A documented GRID option does not require changing an existing CUDA compute SKU to GRID; that separate selection is not changed here.

Isaac Sim evidence and limitations

Isaac Sim v5.1.0's dependency manifest pins Kit SDK 107.3.3. The linked upstream explanation says this Kit version does not support 59x drivers; official requirements list R580-tested drivers.

This is not a guarantee that every Isaac Sim workload works on the exact Azure GRID build. The separate physical-GPU/MIG identifier bug in the NCv6 reproduction requires newer Kit and can persist even with a supported driver. No A10 Isaac Sim renderer run is claimed.

Validation

• Ten Python updater/config tests pass.
• All 22 existing Bats installer tests pass.
• Existing shellcheck command and git diff --check pass.
• Live upstream metadata resolves R580 to 580.178.04 and R595 to 595.91.07, with the official Azure installer URLs.
• The Azure 580.178.04 installer URL returns HTTP 200.
• CI run 37508449970 passed all seven jobs: both GRID image builds, all four CUDA image variants, and lint-and-test.

Required AgentBaker follow-up

There is currently no published R580 tag in mcr.microsoft.com/aks/aks-gpu-grid. Publication from the normal main-branch workflow must happen before AgentBaker can pin a real R580 image.

After publication, update AgentBaker's GPUContainerImages entry to the actual R580 tag and constrain Renovate's aks/aks-gpu-grid updates to R580. Existing R595 tags must not win version selection for the A10 LTS path. Add exact-version GPU E2E assertions and validate the published image before rollout.

This PR does not change AgentBaker, merge existing upgrade PRs, publish from an unmerged branch, or update customer nodes.