Upgrade the stack in a project

1. Confirm the pull request bumps @moifort/stack. Otherwise this skill does not apply.
2. In the pull request's branch: bun install, bunx stack sync, commit chore(stack): sync to <version>.
3. Read the Upgrade part of every CHANGELOG.md section between the two versions (node_modules/@moifort/stack/CHANGELOG.md), then bunx stack migrations <old> <new> --json: the migrations between the two versions, for this project's stacks, in order.
4. For each migration, in order:
   • read the rule it points to and its body (what changes, how to find it, how to fix it, when it does not apply);
   • find the affected code, fix it, run its check command until it exits 0;
   • commit refactor(<scope>): <migration id>;
   • when it does not apply, note why and commit nothing.
5. bun run preflight (and bun run ios:build with the ios stack). A failure caused by a migration: revert that migration's commit and mark it needs review.
6. If the version changed a routine (stack/routines/), update the scheduled task.
7. Comment on the pull request: one line per migration, its outcome (applied, not applicable, needs review) and the files touched.
8. Merge only when every migration is safe, each applied or not applicable, every check passes and CI is green. Otherwise label stack:review and leave it open.

Never edit stack/ by hand, never edit a rule from a project: a wrong rule is reported.