Validate Fleet extension types client-side

[Britania Rodriguez Reyes (britaniar)]

Motivation

Fleet extension operations currently rely on the service to reject unsupported extension types. Since Fleet presently supports only microsoft.flux, fail fast in the CLI before sending ARM requests when another extension type is supplied.

Changes

• Adds microsoft.flux as the supported Fleet extension type constant.
• Validates extension types case-insensitively for Fleet operations where the type is supplied or available:
  • az k8s-extension create
  • az k8s-extension update using the existing resource's extension type
  • az k8s-extension extension-types list-versions-by-location
  • az k8s-extension extension-types show-by-cluster
  • az k8s-extension extension-types list-versions-by-cluster
  • az k8s-extension extension-types show-version-by-cluster
  • Deprecated aliases routed through the same handlers.
• Raises InvalidArgumentValueError before invoking a mutating or discovery ARM request for unsupported types.
• Keeps resource show/list/delete available because they do not accept an extension type; delete intentionally remains a cleanup path for unsupported or legacy resources.
• Normalizes cluster and extension type values at call sites before validation.
• Adds focused tests for all guarded operations, case-insensitive Flux acceptance, and unrestricted deletion.
• Fixes an upstream Python 3.14 pylint warning by making the ChaosStudio platform identity helper's two-item return shape explicit.
• Bumps k8s-extension to 1.9.3 and updates the changelog.

Example

az k8s-extension create \
  --resource-group fleet-rg \
  --cluster-name fleet-1 \
  --cluster-type fleets \
  --name extension-1 \
  --extension-type contoso.extension

Extension type 'contoso.extension' is not supported for cluster type 'fleets'. The supported extension type is 'microsoft.flux'.

Tests

• azdev test test_fleet_support --series — 11 tests and 4 subtests passed
• python -m pytest src/k8s-extension/azext_k8s_extension/tests/latest/test_chaos_studio.py -q — 30 tests and 24 subtests passed
• azdev linter k8s-extension — passed
• azdev style k8s-extension — pylint and flake8 passed
• git diff --check — passed

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[Yong Zhang (yonzhan)]

/azp run

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