Share RUNNER_TEMP with agent step in compiled lock.yml

[Copilot]

RUNNER_TEMP is used extensively in agent step shell scripts (e.g. ${RUNNER_TEMP}/gh-aw/actions/...) but was never explicitly declared in the step's env: block, unlike GITHUB_WORKSPACE which is already explicitly forwarded.

Changes

• All engine execution steps (copilot, claude, codex, gemini, antigravity, crush, opencode, pi): add RUNNER_TEMP: ${{ runner.temp }} to the agent step env: map alongside the existing GITHUB_WORKSPACE entry
• Test: assert RUNNER_TEMP is present in copilot engine step content
• Golden fixtures + lock.yml: regenerated (236 files)

Result in compiled lock.yml:

        env:
          GITHUB_WORKSPACE: ${{ github.workspace }}
          RUNNER_TEMP: ${{ runner.temp }}   # new