v0.10.1

Bug fixes:
- update: 'update available' nag now actually prints. Previous code
  raced itself: a detached goroutine fetched from GitHub while the
  process was already exiting, and NextCheck got bumped *before* the
  fetch even started, suppressing the nag indefinitely. Now uses a
  synchronous, bounded (800ms) check with a disk-cached latest-tag,
  so subsequent runs print the banner with zero network I/O.
- update: pseudo-version builds (v0.0.0-...) and dirty/dev builds are
  now correctly recognized as dev versions and skip the check.
- update: VERS_NO_UPDATE_CHECK / NO_UPDATE_NOTIFIER env vars now
  silence the check (e.g. for CI / scripted use).
- update: banner now writes to stderr so it cannot contaminate
  stdout when piping CLI output through grep/jq/etc.

Cosmetic:
- Stripped emoji and decorative glyphs from CLI output. Status
  messages now use lowercase compiler-style prefixes
  (error: / warning: / note:) matching gcc/rustc/clippy/go.
- ASCII tree drawing for commit lineage display.

PRs: #188, #189