[giscebot]

Summary

• add sastre deploy --simulation for SSH and local targets
• apply the real git am / git apply flow in a detached temporary worktree
• preserve target HEAD, index, working tree, stash, and GitHub deployment metadata
• return exit status 1 when any simulated PR fails
• serialize local simulations/deployments with the same checkout-derived flock path used remotely

Tests

• erp3/bin/python -m pytest -q — 65 passed
• erp2/bin/python -m pytest -q — 65 passed

Includes success/conflict coverage for patch-series and --as-diff simulation, dirty-target preservation, temporary-worktree cleanup, and absence of GitHub deployment/status calls.

Dependency

This PR is intentionally based on #179 because simulations must use the same remote repository lock as real deployments. Merge/rebase onto master after #179 lands.

Closes #196