The BranchStatus intermediate struct is removed. Branch, Detached, and
the []LocalBranchRef slice now live directly on RepoStatus, eliminating
one layer of indirection across all call-sites.

- BranchStatus.Locations removed; checked-out branch data is now
  accessed via RepoStatus.CurrentBranchLocations(), which reads the
  LocalBranchRef with Current: true
- GitBranchStatus() now returns (branch, detached, []LocalBranchRef, error)
  instead of a BranchStatus value
- GitBranchStatus() always produces a Current: true entry, even when
  git for-each-ref does not enumerate the checked-out branch
- FilterLocalOnlyForConfig replaced by RepoStatus.Filter(), which
  preserves the current branch so HEAD/remote comparison is always
  available
- HasLocalRemoteMismatch replaced by HasUnpushedChanges, now scoped
  over all non-hidden branches (not just the current one)
- AlwaysListBranch / branchDefaultAlways replaced with
  slices.Contains(config.Branches.Default, name)
- MultiGitStatus.Set removed; AddResult used everywhere
- RepoStatus.Status (embedded git.Status) removed; porcelain is the
  sole source of dirty-file data
- RepoInclusionReasons and the "w why listed" TUI overlay removed
- New report subcommand (report.go): scans repos and emits JSON plus
  a text summary; --output-file / -o flag writes to a file
- openCurrentRepo changed to cmd.Start() (non-blocking editor launch)
- Debug log.Printf calls and per-repo timing metrics removed