Add release-scenario matrix to upgrade integration test (latest-1..latest-5)

[Copilot]

This updates the upgrade integration workflow to validate gh aw upgrade across multiple recent release starting points instead of a single n-1 path. The workflow now collects latest and runs isolated scenarios for latest-1 through latest-5, while preserving daily execution and issue filing on upgrade failures.

• Release scenario discovery

  • Added a collect-releases job to fetch non-draft releases and emit:
    • latest target tag
    • a JSON matrix of upgrade sources: latest-1..latest-5

• Matrix-based upgrade coverage

  • Converted upgrade-path-test into a scenario matrix.
  • Each matrix run:
    • installs the pinned source release
    • executes gh aw upgrade --pre-releases --no-fix
    • verifies the installed version matches latest

• Failure reporting behavior retained

  • Kept the conclusion job’s failure aggregation and issue creation flow for upgrade errors.
  • Daily schedule trigger remains in place.

strategy:
  fail-fast: false
  matrix:
    scenario: ${{ fromJSON(needs.collect-releases.outputs.scenarios) }}

[pelikhan]

@copilot also matrix through windows/linux/macos image runners