v0.5.0 — Watch-mode categories & robustness hardening

Added

• Watch mode (-w) groups repositories into collapsible category folders.
  Repos are bucketed by their path breadcrumb relative to the scan root, joined
  with a chevron (core › packages); repos directly under the root stay flat,
  and single-repo folders fold back to just the repo name. Category headers
  carry an aggregated status (✓ / ↑ ↓ ●) in the STATUS column and are shown
  in cyan + bold. ↑/↓ move a cursor, Enter expands/collapses, and the
  expand state survives refreshes. Nav hints appear only when categories exist.
• ~/.gitlsrc key categories (default true) — set it to false for one
  flat, alphabetically sorted list in watch mode.
• docs/ROADMAP.md — the plan through 1.0.0.

Changed

• The one-shot status table is now sorted alphabetically by repo name
  (case-insensitive) instead of directory-traversal order, matching watch mode.
  Sorting is display-only — summary counts and column widths are unaffected.
• The watch-mode table is sized to its content instead of being stretched to the
  terminal width; long breadcrumbs overflow the row rather than widening the
  NAME column.
• The watch footer drops the redundant scan path and shows a "dirty only" hint
  while --dirty is active.

Fixed

• run_git_capture() no longer hangs when a child process fills the pipe —
  read() is retried on EINTR. The same applies to waitpid(), which could
  report a spurious clean exit and leave a zombie behind.
• Watch mode handles SIGWINCH: column widths are recomputed and the table is
  redrawn when the terminal is resized.
• SIGINT / SIGTERM / SIGWINCH are blocked in worker threads, so only the
  main thread handles them.
• The watch cursor stays anchored to the selected repo / category across
  rescans.
• Table alignment with wide and zero-width characters: display width is now
  measured with wcwidth-style tables (combining marks = 0, CJK / emoji = 2).
• max_depth from ~/.gitlsrc is validated (errno / INT_MAX), and a bare ~
  as default_dir is expanded.
• The watch footer no longer offers fetch / pull when git is unavailable.
• The footer note is derived from the actual result, so a failed action reads
  "… failed" instead of reporting success.
• usage() prints to stdout for an explicit -h, not to stderr.