Test qa.yaml with starflow PR #101 changes

[Copilot]

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Description

Tests craft-application qa.yaml workflow against starflow PR #101 changes before merging in both repositories.

Changes

• Updated .github/workflows/qa.yaml to reference @copilot/use-pristine-ubuntu-action (the actual branch name from starflow PR feat: do variable expansion when loading project #101) instead of @main for starflow workflows
• Added header comments linking to Add pristine-ubuntu-action to hosted runners starflow#101

All 2 workflow references now point to the PR branch:

• canonical/starflow/.github/workflows/lint-python.yaml@copilot/use-pristine-ubuntu-action
• canonical/starflow/.github/workflows/test-python.yaml@copilot/use-pristine-ubuntu-action

Note: This is temporary for cross-repo validation.

Original prompt

Create a test pull request that evaluates changes to the GitHub Actions workflow qa.yaml, similar to the approach used in canonical/craft-parts#1412. This should include updates or additions that facilitate testing of the workflow or related process, referencing the changes or process established in PR #101 of the starflow project, if applicable. The intent is to validate that the qa.yaml workflow functions properly with those types of updates, similar to what was done in craft-parts.

This pull request was created as a result of the following prompt from Copilot chat.

Create a test pull request that evaluates changes to the GitHub Actions workflow qa.yaml, similar to the approach used in canonical/craft-parts#1412. This should include updates or additions that facilitate testing of the workflow or related process, referencing the changes or process established in PR #101 of the starflow project, if applicable. The intent is to validate that the qa.yaml workflow functions properly with those types of updates, similar to what was done in craft-parts.

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