v5.8.0

Plugin to CLI version lockstep (RDR-143): the conexus plugin and the nx CLI
ship the same version but update through independent channels, so they could
silently drift apart (the root of the recent version-skew incidents). A new
SessionStart hook now keeps them in sync.

Added

• Plugin to CLI version-lockstep hook (RDR-143). A stdlib-only
  SessionStart (matcher startup) hook detects when the installed nx CLI
  is older than the plugin and, on skew, emits a one-line nudge and dispatches
  a detached, extras-preserving upgrade in the background (uv tool upgrade conexus then nx upgrade). The upgrade takes effect on the next session and
  never blocks startup. It skips dev/editable trees (uv-receipt gate), never
  uses a raw uv tool install (which would strip the [local] extra), and
  records ~/.config/nexus/cli_lockstep_marker only after a confirmed upgrade,
  so a failed attempt simply retries next session. Two new hook scripts
  (version_lockstep_hook.py, version_lockstep_action.py) wired into a
  dedicated SessionStart block.