Merging 18 PRs

[jonnii]

This PR merges the following changes:

1. refactor(merge): simplify multistack discovery logic #862 refactor(merge): simplify multistack discovery logic
2. feat(foreach): improve foreach action and add tests #863 feat(foreach): improve foreach action and add tests
3. feat(foreach): add foreach events and dry-run support #864 feat(foreach): add foreach events and dry-run support
4. feat(foreach): add stack range filtering and parallel execution #865 feat(foreach): add stack range filtering and parallel execution
5. feat(restack): improve restack with better CLI flags and add tests #866 feat(restack): improve restack with better CLI flags and add tests
6. docs(cli): update stack-fix agent template #867 docs(cli): update stack-fix agent template
7. docs(cli): update stack-verify agent template #868 docs(cli): update stack-verify agent template
8. docs(cli): update stack-absorb agent template #869 docs(cli): update stack-absorb agent template
9. docs(cli): update stack-sync agent template #870 docs(cli): update stack-sync agent template
10. docs(cli): update stack-status agent template #871 docs(cli): update stack-status agent template
11. docs(cli): update skill templates to use scoped restack commands #872 docs(cli): update skill templates to use scoped restack commands
12. feat(sync): add would_restack_stacks to dry-run JSON for restack planning #873 feat(sync): add would_restack_stacks to dry-run JSON for restack planning
13. feat(foreach): add --all-stacks and --stacks multi-stack scope flags #874 feat(foreach): add --all-stacks and --stacks multi-stack scope flags
14. feat(restack): add --parallel flag to run independent stacks in parallel worktrees #875 feat(restack): add --parallel flag to run independent stacks in parallel worktrees
15. feat(restack): annotate JSON output with stack_root per branch for multi-stack grouping #876 feat(restack): annotate JSON output with stack_root per branch for multi-stack grouping
16. docs: update restack examples to use scoped flags across user-facing docs #877 docs: update restack examples to use scoped flags across user-facing docs
17. fix: harden stack automation error handling #878 fix: harden stack automation error handling
18. docs: clarify would_restack_stacks must be recomputed after sync before restack #880 docs: clarify would_restack_stacks must be recomputed after sync before restack

Stack

main
  └─ jonnii/20260415014309/simplify-multistack-discovery-logic (#862)
    └─ jonnii/20260415014644/improve-foreach-action-and-add-tests (#863)
      └─ jonnii/20260415015107/add-foreach-events-and-dry-run-support (#864)
        └─ jonnii/20260415015552/add-stack-range-filtering-and-parallel-execution (#865)
          └─ jonnii/20260415020529/improve-restack-with-better-CLI-flags-and-add (#866)
            └─ jonnii/20260415021035/update-stack-fix-agent-template (#867)
              └─ jonnii/20260415022132/update-stack-verify-agent-template (#868)
                └─ jonnii/20260415022435/update-stack-absorb-agent-template (#869)
                  └─ jonnii/20260415022653/update-stack-sync-agent-template (#870)
                    └─ jonnii/20260415022842/update-stack-status-agent-template (#871)
                      └─ jonnii/20260415023903/update-skill-templates-to-use-scoped-restack (#872)
                        └─ jonnii/20260415024545/add-would_restack_stacks-to-dry-run-JSON-for (#873)
                          └─ jonnii/20260415025350/add-all-stacks-and-stacks-multi-stack-scope (#874)
                            └─ jonnii/20260421200717/add-parallel-flag-to-run-independent-stacks-in (#875)
                              └─ jonnii/20260421201736/annotate-JSON-output-with-stack_root-per-branch (#876)
                                └─ jonnii/20260421202331/update-restack-examples-to-use-scoped-flags (#877)
                                  └─ jonnii/20260421204210/harden-stack-automation-error-handling (#878)
                                    └─ jonnii/20260422221327/clarify-would_restack_stacks-must-be-recomputed (#880)

Stackit-Stack-Size: 18
Stackit-PRs: 862,863,864,865,866,867,868,869,870,871,872,873,874,875,876,877,878,880