* fix(config): validate sync-branch at config time
Add sync-branch validation to validateYamlConfigValue() to reject
main/master at config time, preventing the validation bypass in GH#1166.
- Add case for sync-branch and sync.branch keys
- Inline validation logic to avoid import cycle (config <-> syncbranch)
- Add unit tests for rejection (main/master) and acceptance (valid names)
Part of: #1166
* fix(sync): add runtime guard for sync-branch == current-branch
Add dynamic runtime check before worktree operations to catch cases
where sync-branch matches the current branch. This provides defense
in depth for manual YAML edits, pre-fix configs, or non-main/master
branch names (trunk, develop, production, etc.).
- Check IsSyncBranchSameAsCurrent() after hasSyncBranchConfig is set
- Position check BEFORE worktree entry (CWD changes inside worktree)
- Add integration test TestSync_FailsWhenOnSyncBranch
Part of: #1166
* docs: note main/master restriction in sync-branch FAQ
Clarifies that git worktrees cannot checkout the same branch in
multiple locations, so main/master cannot be used as sync branch.
2cbf3a5497