fix(coordination): count assigned ready-group beads as claims; honour status_groups.ready (GH #519)

A bead sent back to a ready-group status such as rework keeps its assignee,
so br ready offers it while every other agent's --claim is refused, yet
br coordination status listed in_progress beads only and never saw it, and
its ready count ignored workflow.status_groups.ready.

Claims are now every in-progress bead plus every assigned bead in any other
non-terminal, non-deferred status; workspace.ready uses the configured
ready group exactly as br ready does; workspace.in_progress is the real
in_progress count.

Test: coordination_status_sees_assigned_rework_and_honours_ready_group.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>