Fix split subscription SDK import

[TacoRocket]

Summary

• switch AzureFox to the split Azure subscriptions management package for
• add the new default dependency so editable installs include the runtime requirement
• cover the import layout with a focused client factory regression test

Verification

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• {
  "effective_scopes": [
  {
  "display_name": "Azure Personal Lab",
  "id": "/subscriptions/b436881a-b87e-44b6-a5d6-7bf7f4bc9c88",
  "scope_type": "subscription"
  }
  ],
  "issues": [],
  "metadata": {
  "auth_mode": "azure_cli_user",
  "command": "whoami",
  "devops_organization": null,
  "generated_at": "2026-04-18T00:30:01.661302Z",
  "schema_version": "1.4.0",
  "subscription_id": "b436881a-b87e-44b6-a5d6-7bf7f4bc9c88",
  "tenant_id": "0bdb6f5d-f8c3-4525-8417-b1fa701482cd",
  "token_source": "azure_cli"
  },
  "principal": {
  "display_name": "Colby Farley",
  "id": "1058bd62-c9bd-4332-b6c4-bcf3f90f1c4e",
  "principal_type": "User",
  "tenant_id": "0bdb6f5d-f8c3-4525-8417-b1fa701482cd"
  },
  "subscription": {
  "display_name": "Azure Personal Lab",
  "id": "b436881a-b87e-44b6-a5d6-7bf7f4bc9c88",
  "state": "Enabled"
  },
  "tenant_id": "0bdb6f5d-f8c3-4525-8417-b1fa701482cd"
  }

Note

• repo-preferred CCR was not run because this session does not permit subagent delegation unless explicitly requested