Replace shell `\&\&` and `||` operators in execCommand calls with
TypeScript control flow. This fixes re-integrate commits failing when
the user's default shell is Nushell, which does not support `\&\&`.
Changes:
- createTempWorktree: split `mkdir \&\& mktemp` into two calls
- ensureLocalBranch: use isOk() instead of `echo ok || echo missing`
- isCherryPickInProgress: use isOk() instead of `echo yes || echo no`
Closes#870
jwcrystal
291d00de8b