Fix transient errors in nightly rad CLI tests workflow

[Copilot]

Description

The nightly rad CLI tests workflow was experiencing transient failures when calling the GitHub releases API. Two issues:

1. The API was called 6 times (once per OS/arch matrix combination), increasing rate limit exposure
2. When parsing failed, no debug output was shown—making failures impossible to diagnose

Changes:

• Single API call: New get-version job fetches the release version once, passes it to matrix jobs via output
• Error visibility: When version parsing fails, the first 50 lines of the API response are echoed
• Reliable parsing: Replaced fragile grep | awk | sed pipeline with jq
• Script simplification: test-cli-download.sh now requires RAD_VERSION as a parameter (no longer makes its own API call)

# Before: API called in each matrix job via shell script
- name: Test CLI download
  run: make test-cli-download OS=${{ matrix.os }} ...

# After: Version fetched once, passed to matrix jobs
get-version:
  outputs:
    rad_version: ${{ steps.get-version.outputs.rad_version }}
    
download:
  needs: get-version
  run: make test-cli-download ... RAD_VERSION=${{ needs.get-version.outputs.rad_version }}

Type of change

• This pull request is a minor refactor, code cleanup, test improvement, or other maintenance task and doesn't change the functionality of Radius (issue link optional).

Contributor checklist

Please verify that the PR meets the following requirements, where applicable:

• An overview of proposed schema changes is included in a linked GitHub issue.
  • Yes
  • Not applicable
• A design document PR is created in the design-notes repository, if new APIs are being introduced.
  • Yes
  • Not applicable
• The design document has been reviewed and approved by Radius maintainers/approvers.
  • Yes
  • Not applicable
• A PR for the samples repository is created, if existing samples are affected by the changes in this PR.
  • Yes
  • Not applicable
• A PR for the documentation repository is created, if the changes in this PR affect the documentation or any user facing updates are made.
  • Yes
  • Not applicable
• A PR for the recipes repository is created, if existing recipes are affected by the changes in this PR.
  • Yes
  • Not applicable

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[brooke-hamilton]

@copilot why are you calling the GitHub API in both the workflow and the script? I think you should call it once only.

[Copilot]

Good point. Removed the GitHub API call from the shell script in 7437d01. The API is now called only once in the workflow's get-version job, and the script requires RAD_VERSION to be passed as a parameter.