v0.6.0

Added

• The lead picks plugin skills per sub-task: it sees the skills of the enabled
  plugins and a built-in catalog of installable plugins, lists only the skills
  each sub-task needs (skills in the split) and may ask for plugins that are
  not installed or disabled. Unknown skills and plugins are dropped.
• Nodes keep their skills: they are added to the role's own skills when the
  node runs, shown in the inspector as (role), (lead) or (not installed),
  and editable with K on a todo or failed node.
• Plugin requests: after a split the Workspace asks, per plugin, whether to
  install (or enable) it (y, n, a skips all). /plugin available lists
  the catalog and /plugin install <name> installs a catalog plugin after the
  same confirmation. Installs use git (shallow clone into
  ~/.decsr/plugin-src) and only ever come from the built-in catalog.