Refactors GitHub Actions workflow setup into a reusable composite action, consolidating repeated setup logic across CI, mobile, release, test-release, and version workflows (176 lines removed). Adds corresponding tests for the workflow configuration.
Fusion-Task-Id: FN-4100
Fixes overlap merge checkout logic by removing the composite checkout approach and replacing it with explicit workflow-specific checkout steps, with a new CI job to guard against regressions and a test hardening the temporary directory cleanup path.
Fusion-Task-Id: FN-4157
FN-4093 introduced a reusable `setup-node-pnpm` composite GitHub Action and refactored the PR checks workflow to use it, reducing the workflow file by over 60 lines while adding a contract test for the action. A small follow-up stabilizes workspace quality gates by adding an export in the core store
Fusion-Task-Id: FN-4093
