Fix composite action output reference in build-test workflow

[Copilot]

The workflow referenced steps.cli-path.outputs.path directly, but cli-path was an internal step within the composite action setup-copilot. Composite actions require explicit output declarations.

Changes

• .github/actions/setup-copilot/action.yml: Added outputs section declaring cli-path output
• .github/workflows/build-test.yml: Added id: setup-copilot to composite action step and updated reference to steps.setup-copilot.outputs.cli-path

Before

steps:
  - uses: ./.github/actions/setup-copilot
  - name: Run Java SDK tests
    env:
      COPILOT_CLI_PATH: ${{ steps.cli-path.outputs.path }}

After

steps:
  - id: setup-copilot
    uses: ./.github/actions/setup-copilot
  - name: Run Java SDK tests
    env:
      COPILOT_CLI_PATH: ${{ steps.setup-copilot.outputs.cli-path }}

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.